biology lab hypothesis example

Demonstration of a close genetic relationship between human and chimpanzee through the Nutall precipitation reaction

Some scientists theorize that humans and chimpanzees evolved from a common ancestor millions of years ago. Because of this theory, we hypothesized that the chimpanzee blood proteins would most resemble human blood proteins. Three other vertebrates, the frog, cow, and monkey were also compared in this study. In order to test for similarities in various blood proteins, the Nutall Precipitation process was used. By employing this technique, we noted and compared the agglutination of red blood cells from the five species. This method allowed us to see which animal’s blood proteins would be most closely related to humans. Results confirmed our hypothesis: the blood proteins of chimpanzees are most closely related to human blood proteins, more so than to the blood proteins of a cow, a frog, and a monkey.

The Nutall Precipitation is a technique used to test and compare the relationship of the blood proteins between one species and another to see how they are similar or different. The Nutall Precipitation capitalizes on the vertebrates’ immune defense mechanism, which resists foreign materials that are introduced into their blood (Braun, pp. 71). To combat the foreign materials, the vertebrates will develop antibodies which, in turn, will agglutinate to the foreign material. The agglutination causes a fast precipitation reaction (Braun, pp. 71). By judging the agglutination amounts, we can determine if the materials are more or less foreign to the blood. The Nutall Precipitation can attempt to prove or disprove the hypothesis that the chimpanzee is the animal that is most closely related to a human. An anti-human serum was introduced into the blood proteins of the chimpanzee, cow, frog, and the monkey. The agglutination reactions allowed us to determine which of the four animals was the one most closely related to a human. When there is an increase in agglutination between the animal and human blood, it signifies that the two species’ blood is more similar, thus showing a closer relationship. When the agglutination is lighter, it signifies that the blood proteins in human blood and animal blood are less similar, thus determining that the two species are not as closely related. In our experiment using the Nutall Precipitation, our hypothesis that the chimpanzee is the animal most closely related to humans was tested to determine whether or not the chimpanzee’s agglutination with the human blood is greater than with the other species-the cow, frog, and the monkey.

Methodology

The Nutall Precipitation technique tested the hypothesis-five dishes were set up, each one with a different serum from a chimpanzee, cow, frog, monkey, and a human. The dish with the anti-human serum was compared with the four dishes of animal serum. In each dish, there were eight wells containing serial dilutions of a specific animal serum (50 – 300 l) and a combination of water (100 – 350 l) and anti-human serum (400 l). Data was recorded based on the amount of agglutination in each dish. A table chart was developed, using the rubric scores of 0, 1, 2, and 3. A score of 0 signified that there was no reaction between the anti-human serum and animal serum. A score of 1 indicated that there was a reaction, but that it was light and weak. A score of 2 meant that there was a medium reaction, showing signs of agglutination. A score of 3 signified that there was high agglutination with a strong and immediate reaction.

Results and Discussion

Well Number:

Based on the recorded data, the dish containing the chimpanzee serum showed an immediate and strong reaction with the human’s anti-serum with the heaviest agglutination in comparison to the other species. In fact, the dishes containing the chimpanzee’s serum and the anti-human serum showed the same amounts of agglutination. The monkey was shown to be trailing the chimpanzee, with the cow next. The frog showed the least amount of agglutination, with wells 3 through 8 showing no signs of agglutination. The conclusion strongly indicates that the sera of the chimpanzee and humans showed very similar agglutination reactions with the anti-human serum. This supports our hypothesis that the chimpanzee blood protein is the most closely related to the human blood protein as compared to the blood proteins of a cow, a frog, and a monkey.

Bibliography

Braun DC and Pearce LL, Laboratory Manual for Introduction to Biology. 5th ed. Washington (DC): Gallaudet University; 2004: 69 – 75

Olson MV and Varki A. Sequencing the chimpanzee genome: insights into human evolution and disease Nature Reviews Genetics. 2003 Jan 01;4:20-28.

****This sample biology lab report was developed by Will Garrow for a biology course at Gallaudet University. It was revised by Raymond Merritt and Jane Dillehay of the Department of Biology.

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Biology 116 Lab Manual

Statement of hypothesis.

A hypothesis is an unproven explanation for the observed phenomena. In its simplest form, a hypothesis is an "educated guess" or intuitive hunch that is proposed as a possible answer to the question you're interested in answering. There's a couple of things to know about hypothesis building before you get started:

A hypothesis is not a question, it is a statement

For example, "over a given time period, plants will grow taller at higher temperatures" is a hypothesis, whereas "over a given time period, will plants grow taller at a higher temperature?" is a question. They're generally related, but they're not the same.

A hypothesis must be testable

The hypothesis does not need to be "correct" (after all, there's really no way to know that at this point) but you do have to be able to test whether it is correct or not. In our example from above, we can test the hypothesis by growing the plants at different temperatures, and measuring their heights after a set amount of time. Thus, we have a way to measure the effect of interest and test our hypothesis.

A hypothesis comes before the experiment, not the other way around

We call this an a priori hypothesis , meaning that we made the hypothesis before we ran the experiment and learned the answer. Sometimes, because we want to show that we knew what we were doing, we feel the need to change the hypothesis we started with, so that it better reflects the results we got. This is known as HARKing (Hypothesizing After Results are Known), and is not considered to be good science. It's important to present your hypothesis as you originally developed it, and then discuss what you have learned about the topic based on your testing of that hypothesis.

Optional Lab Activities

Scientific method lab report.

The report should be typed and single spaced. See grading rubric at the end of this page for clarity on formatting.

Requirements

Should include Title (brief, concise, yet descriptive), your name, lab instructor’s name, and lab section (such as L14 or L24, etc.).

Note: this is a separate sheet

Body of Report

Identify the different sections of the body of the report with headings.

• The report should begin with a brief paragraph (complete sentences) that includes a statement of the problem and your hypothesis (remember your hypothesis should be written as a testable statement).
• What question are you trying to answer?
• Include any preliminary observations or background information about the subject (in this case the Alka-Seltzer tablet) such as what the tablet is used for, directions on packaging, personal experience you may have, etc. Be sure to cite any sources.
• Write a possible explanation/prediction for the problem/question you are asking.
• Make sure this possible explanation/prediction is a complete sentence and not a question.
• Make sure the statement is testable. In other words, can you perform an experiment that will either support or refute your prediction. If you cannot not think of a way to test your prediction, then it is not testable.
• Make a list (this does not need to be in paragraph form) of all  items used in the experiment and their quantities. Of the materials used, identify which are dependent and independent variables, constants (standardized variable) and control group (you will lose points if you do not identify all  dependent and independent variables, constants and controls) .
• Write at least one paragraph (complete sentences) which explains what you did in the experiment.
• Your procedure should be written so that anyone else could repeat the experiment. For instance, if you used hot water, how did you make the water hot and what temperature was it; if you chose salt water, what was the concentration of the salt water, etc. That means that even some of the most obvious steps need to be stated so there is no uncertainty.
• When designing the procedure, be sure to include replicating the experiment (trials) to ensure data is reproducible and valid.
• Write at least a paragraph (complete sentences) describing the results and observations of your experiment. Here you will compare results for control groups and experimental groups and not simply list the numbers.
• This section also includes both  a data table and graph to illustrate the results of you experiment. Be sure to include calculated averages of trials.
• All tables, graphs and charts should be labeled appropriately (a title, labels for x & y axis, legend etc.) so the reader will be able to understand the information presented.
• Write at least a paragraph restating your hypothesis and whether you accept or reject your hypothesis
• In this section, explain  why you accepted or rejected your hypothesis using data from the experiment . Include a brief summary of the data—averages, highest, lowest, etc., to help the reader understand your results and why you have come to particular conclusions.
• Discuss your thoughts about the possible reasons for your results (for example, if you chose salt water as a variable, give a possible reason why salt water, in particular, may have generated your results).
• Discuss possible errors that could have occurred in the collection of the data (experimental errors) and describe how these errors may have impacted the data.

Sample Report

This is a good lab report written for a different (and more complex experiment). You can use it as a model if you want.

Lab Report Grading Rubric

• Biology 101 Labs . Authored by : Lynette Hauser. Provided by : Tidewater Community College . Located at : http://www.tcc.edu/ . License : CC BY: Attribution

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How To Write A Lab Report | Step-by-Step Guide & Examples

Published on May 20, 2021 by Pritha Bhandari . Revised on July 23, 2023.

A lab report conveys the aim, methods, results, and conclusions of a scientific experiment. The main purpose of a lab report is to demonstrate your understanding of the scientific method by performing and evaluating a hands-on lab experiment. This type of assignment is usually shorter than a research paper .

Lab reports are commonly used in science, technology, engineering, and mathematics (STEM) fields. This article focuses on how to structure and write a lab report.

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Table of contents

Structuring a lab report, introduction, other interesting articles, frequently asked questions about lab reports.

The sections of a lab report can vary between scientific fields and course requirements, but they usually contain the purpose, methods, and findings of a lab experiment .

Each section of a lab report has its own purpose.

• Title: expresses the topic of your study
• Abstract : summarizes your research aims, methods, results, and conclusions
• Introduction: establishes the context needed to understand the topic
• Method: describes the materials and procedures used in the experiment
• Results: reports all descriptive and inferential statistical analyses
• Discussion: interprets and evaluates results and identifies limitations
• Conclusion: sums up the main findings of your experiment
• References: list of all sources cited using a specific style (e.g. APA )
• Appendices : contains lengthy materials, procedures, tables or figures

Although most lab reports contain these sections, some sections can be omitted or combined with others. For example, some lab reports contain a brief section on research aims instead of an introduction, and a separate conclusion is not always required.

If you’re not sure, it’s best to check your lab report requirements with your instructor.

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Your title provides the first impression of your lab report – effective titles communicate the topic and/or the findings of your study in specific terms.

Create a title that directly conveys the main focus or purpose of your study. It doesn’t need to be creative or thought-provoking, but it should be informative.

• The effects of varying nitrogen levels on tomato plant height.
• Testing the universality of the McGurk effect.
• Comparing the viscosity of common liquids found in kitchens.

An abstract condenses a lab report into a brief overview of about 150–300 words. It should provide readers with a compact version of the research aims, the methods and materials used, the main results, and the final conclusion.

Think of it as a way of giving readers a preview of your full lab report. Write the abstract last, in the past tense, after you’ve drafted all the other sections of your report, so you’ll be able to succinctly summarize each section.

To write a lab report abstract, use these guiding questions:

• What is the wider context of your study?
• What research question were you trying to answer?
• How did you perform the experiment?
• What did your results show?
• How did you interpret your results?
• What is the importance of your findings?

Nitrogen is a necessary nutrient for high quality plants. Tomatoes, one of the most consumed fruits worldwide, rely on nitrogen for healthy leaves and stems to grow fruit. This experiment tested whether nitrogen levels affected tomato plant height in a controlled setting. It was expected that higher levels of nitrogen fertilizer would yield taller tomato plants.

Levels of nitrogen fertilizer were varied between three groups of tomato plants. The control group did not receive any nitrogen fertilizer, while one experimental group received low levels of nitrogen fertilizer, and a second experimental group received high levels of nitrogen fertilizer. All plants were grown from seeds, and heights were measured 50 days into the experiment.

The effects of nitrogen levels on plant height were tested between groups using an ANOVA. The plants with the highest level of nitrogen fertilizer were the tallest, while the plants with low levels of nitrogen exceeded the control group plants in height. In line with expectations and previous findings, the effects of nitrogen levels on plant height were statistically significant. This study strengthens the importance of nitrogen for tomato plants.

Your lab report introduction should set the scene for your experiment. One way to write your introduction is with a funnel (an inverted triangle) structure:

• Start with the broad, general research topic
• Narrow your topic down your specific study focus
• End with a clear research question

Begin by providing background information on your research topic and explaining why it’s important in a broad real-world or theoretical context. Describe relevant previous research on your topic and note how your study may confirm it or expand it, or fill a gap in the research field.

This lab experiment builds on previous research from Haque, Paul, and Sarker (2011), who demonstrated that tomato plant yield increased at higher levels of nitrogen. However, the present research focuses on plant height as a growth indicator and uses a lab-controlled setting instead.

Next, go into detail on the theoretical basis for your study and describe any directly relevant laws or equations that you’ll be using. State your main research aims and expectations by outlining your hypotheses .

Based on the importance of nitrogen for tomato plants, the primary hypothesis was that the plants with the high levels of nitrogen would grow the tallest. The secondary hypothesis was that plants with low levels of nitrogen would grow taller than plants with no nitrogen.

Your introduction doesn’t need to be long, but you may need to organize it into a few paragraphs or with subheadings such as “Research Context” or “Research Aims.”

A lab report Method section details the steps you took to gather and analyze data. Give enough detail so that others can follow or evaluate your procedures. Write this section in the past tense. If you need to include any long lists of procedural steps or materials, place them in the Appendices section but refer to them in the text here.

You should describe your experimental design, your subjects, materials, and specific procedures used for data collection and analysis.

Experimental design

Briefly note whether your experiment is a within-subjects  or between-subjects design, and describe how your sample units were assigned to conditions if relevant.

A between-subjects design with three groups of tomato plants was used. The control group did not receive any nitrogen fertilizer. The first experimental group received a low level of nitrogen fertilizer, while the second experimental group received a high level of nitrogen fertilizer.

Describe human subjects in terms of demographic characteristics, and animal or plant subjects in terms of genetic background. Note the total number of subjects as well as the number of subjects per condition or per group. You should also state how you recruited subjects for your study.

List the equipment or materials you used to gather data and state the model names for any specialized equipment.

List of materials

35 Tomato seeds

15 plant pots (15 cm tall)

Light lamps (50,000 lux)

Nitrogen fertilizer

Measuring tape

Describe your experimental settings and conditions in detail. You can provide labelled diagrams or images of the exact set-up necessary for experimental equipment. State how extraneous variables were controlled through restriction or by fixing them at a certain level (e.g., keeping the lab at room temperature).

Light levels were fixed throughout the experiment, and the plants were exposed to 12 hours of light a day. Temperature was restricted to between 23 and 25℃. The pH and carbon levels of the soil were also held constant throughout the experiment as these variables could influence plant height. The plants were grown in rooms free of insects or other pests, and they were spaced out adequately.

Your experimental procedure should describe the exact steps you took to gather data in chronological order. You’ll need to provide enough information so that someone else can replicate your procedure, but you should also be concise. Place detailed information in the appendices where appropriate.

In a lab experiment, you’ll often closely follow a lab manual to gather data. Some instructors will allow you to simply reference the manual and state whether you changed any steps based on practical considerations. Other instructors may want you to rewrite the lab manual procedures as complete sentences in coherent paragraphs, while noting any changes to the steps that you applied in practice.

If you’re performing extensive data analysis, be sure to state your planned analysis methods as well. This includes the types of tests you’ll perform and any programs or software you’ll use for calculations (if relevant).

First, tomato seeds were sown in wooden flats containing soil about 2 cm below the surface. Each seed was kept 3-5 cm apart. The flats were covered to keep the soil moist until germination. The seedlings were removed and transplanted to pots 8 days later, with a maximum of 2 plants to a pot. Each pot was watered once a day to keep the soil moist.

The nitrogen fertilizer treatment was applied to the plant pots 12 days after transplantation. The control group received no treatment, while the first experimental group received a low concentration, and the second experimental group received a high concentration. There were 5 pots in each group, and each plant pot was labelled to indicate the group the plants belonged to.

50 days after the start of the experiment, plant height was measured for all plants. A measuring tape was used to record the length of the plant from ground level to the top of the tallest leaf.

In your results section, you should report the results of any statistical analysis procedures that you undertook. You should clearly state how the results of statistical tests support or refute your initial hypotheses.

The main results to report include:

• any descriptive statistics
• statistical test results
• the significance of the test results
• estimates of standard error or confidence intervals

The mean heights of the plants in the control group, low nitrogen group, and high nitrogen groups were 20.3, 25.1, and 29.6 cm respectively. A one-way ANOVA was applied to calculate the effect of nitrogen fertilizer level on plant height. The results demonstrated statistically significant ( p = .03) height differences between groups.

Next, post-hoc tests were performed to assess the primary and secondary hypotheses. In support of the primary hypothesis, the high nitrogen group plants were significantly taller than the low nitrogen group and the control group plants. Similarly, the results supported the secondary hypothesis: the low nitrogen plants were taller than the control group plants.

These results can be reported in the text or in tables and figures. Use text for highlighting a few key results, but present large sets of numbers in tables, or show relationships between variables with graphs.

You should also include sample calculations in the Results section for complex experiments. For each sample calculation, provide a brief description of what it does and use clear symbols. Present your raw data in the Appendices section and refer to it to highlight any outliers or trends.

The Discussion section will help demonstrate your understanding of the experimental process and your critical thinking skills.

In this section, you can:

• Interpret your results
• Compare your findings with your expectations
• Identify any sources of experimental error
• Explain any unexpected results
• Suggest possible improvements for further studies

Interpreting your results involves clarifying how your results help you answer your main research question. Report whether your results support your hypotheses.

• Did you measure what you sought out to measure?
• Were your analysis procedures appropriate for this type of data?

Compare your findings with other research and explain any key differences in findings.

• Are your results in line with those from previous studies or your classmates’ results? Why or why not?

An effective Discussion section will also highlight the strengths and limitations of a study.

• Did you have high internal validity or reliability?
• How did you establish these aspects of your study?

When describing limitations, use specific examples. For example, if random error contributed substantially to the measurements in your study, state the particular sources of error (e.g., imprecise apparatus) and explain ways to improve them.

The results support the hypothesis that nitrogen levels affect plant height, with increasing levels producing taller plants. These statistically significant results are taken together with previous research to support the importance of nitrogen as a nutrient for tomato plant growth.

However, unlike previous studies, this study focused on plant height as an indicator of plant growth in the present experiment. Importantly, plant height may not always reflect plant health or fruit yield, so measuring other indicators would have strengthened the study findings.

Another limitation of the study is the plant height measurement technique, as the measuring tape was not suitable for plants with extreme curvature. Future studies may focus on measuring plant height in different ways.

The main strengths of this study were the controls for extraneous variables, such as pH and carbon levels of the soil. All other factors that could affect plant height were tightly controlled to isolate the effects of nitrogen levels, resulting in high internal validity for this study.

Your conclusion should be the final section of your lab report. Here, you’ll summarize the findings of your experiment, with a brief overview of the strengths and limitations, and implications of your study for further research.

Some lab reports may omit a Conclusion section because it overlaps with the Discussion section, but you should check with your instructor before doing so.

If you want to know more about AI for academic writing, AI tools, or fallacies make sure to check out some of our other articles with explanations and examples or go directly to our tools!

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A lab report conveys the aim, methods, results, and conclusions of a scientific experiment . Lab reports are commonly assigned in science, technology, engineering, and mathematics (STEM) fields.

The purpose of a lab report is to demonstrate your understanding of the scientific method with a hands-on lab experiment. Course instructors will often provide you with an experimental design and procedure. Your task is to write up how you actually performed the experiment and evaluate the outcome.

In contrast, a research paper requires you to independently develop an original argument. It involves more in-depth research and interpretation of sources and data.

A lab report is usually shorter than a research paper.

The sections of a lab report can vary between scientific fields and course requirements, but it usually contains the following:

• Abstract: summarizes your research aims, methods, results, and conclusions
• References: list of all sources cited using a specific style (e.g. APA)
• Appendices: contains lengthy materials, procedures, tables or figures

The results chapter or section simply and objectively reports what you found, without speculating on why you found these results. The discussion interprets the meaning of the results, puts them in context, and explains why they matter.

In qualitative research , results and discussion are sometimes combined. But in quantitative research , it’s considered important to separate the objective results from your interpretation of them.

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Biology archive

Course: biology archive   >   unit 1, the scientific method.

• Controlled experiments
• The scientific method and experimental design

Introduction

• Make an observation.
• Ask a question.
• Form a hypothesis , or testable explanation.
• Make a prediction based on the hypothesis.
• Test the prediction.
• Iterate: use the results to make new hypotheses or predictions.

Scientific method example: Failure to toast

1. make an observation., 2. ask a question., 3. propose a hypothesis., 4. make predictions., 5. test the predictions..

• If the toaster does toast, then the hypothesis is supported—likely correct.
• If the toaster doesn't toast, then the hypothesis is not supported—likely wrong.

Logical possibility

Practical possibility, building a body of evidence, 6. iterate..

• If the hypothesis was supported, we might do additional tests to confirm it, or revise it to be more specific. For instance, we might investigate why the outlet is broken.
• If the hypothesis was not supported, we would come up with a new hypothesis. For instance, the next hypothesis might be that there's a broken wire in the toaster.

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Hypothesis n., plural: hypotheses [/haɪˈpɑːθəsɪs/] Definition: Testable scientific prediction

Table of Contents

What Is Hypothesis?

A scientific hypothesis is a foundational element of the scientific method . It’s a testable statement proposing a potential explanation for natural phenomena. The term hypothesis means “little theory” . A hypothesis is a short statement that can be tested and gives a possible reason for a phenomenon or a possible link between two variables . In the setting of scientific research, a hypothesis is a tentative explanation or statement that can be proven wrong and is used to guide experiments and empirical research.

It is an important part of the scientific method because it gives a basis for planning tests, gathering data, and judging evidence to see if it is true and could help us understand how natural things work. Several hypotheses can be tested in the real world, and the results of careful and systematic observation and analysis can be used to support, reject, or improve them.

Researchers and scientists often use the word hypothesis to refer to this educated guess . These hypotheses are firmly established based on scientific principles and the rigorous testing of new technology and experiments .

For example, in astrophysics, the Big Bang Theory is a working hypothesis that explains the origins of the universe and considers it as a natural phenomenon. It is among the most prominent scientific hypotheses in the field.

“The scientific method: steps, terms, and examples” by Scishow:

Biology definition: A hypothesis  is a supposition or tentative explanation for (a group of) phenomena, (a set of) facts, or a scientific inquiry that may be tested, verified or answered by further investigation or methodological experiment. It is like a scientific guess . It’s an idea or prediction that scientists make before they do experiments. They use it to guess what might happen and then test it to see if they were right. It’s like a smart guess that helps them learn new things. A scientific hypothesis that has been verified through scientific experiment and research may well be considered a scientific theory .

Etymology: The word “hypothesis” comes from the Greek word “hupothesis,” which means “a basis” or “a supposition.” It combines “hupo” (under) and “thesis” (placing). Synonym:   proposition; assumption; conjecture; postulate Compare:   theory See also: null hypothesis

Characteristics Of Hypothesis

A useful hypothesis must have the following qualities:

• It should never be written as a question.
• You should be able to test it in the real world to see if it’s right or wrong.
• It needs to be clear and exact.
• It should list the factors that will be used to figure out the relationship.
• It should only talk about one thing. You can make a theory in either a descriptive or form of relationship.
• It shouldn’t go against any natural rule that everyone knows is true. Verification will be done well with the tools and methods that are available.
• It should be written in as simple a way as possible so that everyone can understand it.
• It must explain what happened to make an answer necessary.
• It should be testable in a fair amount of time.
• It shouldn’t say different things.

Sources Of Hypothesis

Sources of hypothesis are:

• Patterns of similarity between the phenomenon under investigation and existing hypotheses.
• Insights derived from prior research, concurrent observations, and insights from opposing perspectives.
• The formulations are derived from accepted scientific theories and proposed by researchers.
• In research, it’s essential to consider hypothesis as different subject areas may require various hypotheses (plural form of hypothesis). Researchers also establish a significance level to determine the strength of evidence supporting a hypothesis.
• Individual cognitive processes also contribute to the formation of hypotheses.

One hypothesis is a tentative explanation for an observation or phenomenon. It is based on prior knowledge and understanding of the world, and it can be tested by gathering and analyzing data. Observed facts are the data that are collected to test a hypothesis. They can support or refute the hypothesis.

For example, the hypothesis that “eating more fruits and vegetables will improve your health” can be tested by gathering data on the health of people who eat different amounts of fruits and vegetables. If the people who eat more fruits and vegetables are healthier than those who eat less fruits and vegetables, then the hypothesis is supported.

Hypotheses are essential for scientific inquiry. They help scientists to focus their research, to design experiments, and to interpret their results. They are also essential for the development of scientific theories.

Types Of Hypothesis

In research, you typically encounter two types of hypothesis: the alternative hypothesis (which proposes a relationship between variables) and the null hypothesis (which suggests no relationship).

Simple Hypothesis

It illustrates the association between one dependent variable and one independent variable. For instance, if you consume more vegetables, you will lose weight more quickly. Here, increasing vegetable consumption is the independent variable, while weight loss is the dependent variable.

Complex Hypothesis

It exhibits the relationship between at least two dependent variables and at least two independent variables. Eating more vegetables and fruits results in weight loss, radiant skin, and a decreased risk of numerous diseases, including heart disease.

Directional Hypothesis

It shows that a researcher wants to reach a certain goal. The way the factors are related can also tell us about their nature. For example, four-year-old children who eat well over a time of five years have a higher IQ than children who don’t eat well. This shows what happened and how it happened.

Non-directional Hypothesis

When there is no theory involved, it is used. It is a statement that there is a connection between two variables, but it doesn’t say what that relationship is or which way it goes.

Null Hypothesis

It says something that goes against the theory. It’s a statement that says something is not true, and there is no link between the independent and dependent factors. “H 0 ” represents the null hypothesis.

Associative and Causal Hypothesis

When a change in one variable causes a change in the other variable, this is called the associative hypothesis . The causal hypothesis, on the other hand, says that there is a cause-and-effect relationship between two or more factors.

Examples Of Hypothesis

Examples of simple hypotheses:

• Students who consume breakfast before taking a math test will have a better overall performance than students who do not consume breakfast.
• Students who experience test anxiety before an English examination will get lower scores than students who do not experience test anxiety.
• Motorists who talk on the phone while driving will be more likely to make errors on a driving course than those who do not talk on the phone, is a statement that suggests that drivers who talk on the phone while driving are more likely to make mistakes.

Examples of a complex hypothesis:

• Individuals who consume a lot of sugar and don’t get much exercise are at an increased risk of developing depression.
• Younger people who are routinely exposed to green, outdoor areas have better subjective well-being than older adults who have limited exposure to green spaces, according to a new study.
• Increased levels of air pollution led to higher rates of respiratory illnesses, which in turn resulted in increased costs for healthcare for the affected communities.

Examples of Directional Hypothesis:

• The crop yield will go up a lot if the amount of fertilizer is increased.
• Patients who have surgery and are exposed to more stress will need more time to get better.
• Increasing the frequency of brand advertising on social media will lead to a significant increase in brand awareness among the target audience.

Examples of Non-Directional Hypothesis (or Two-Tailed Hypothesis):

• The test scores of two groups of students are very different from each other.
• There is a link between gender and being happy at work.
• There is a correlation between the amount of caffeine an individual consumes and the speed with which they react.

Examples of a null hypothesis:

• Children who receive a new reading intervention will have scores that are different than students who do not receive the intervention.
• The results of a memory recall test will not reveal any significant gap in performance between children and adults.
• There is not a significant relationship between the number of hours spent playing video games and academic performance.

Examples of Associative Hypothesis:

• There is a link between how many hours you spend studying and how well you do in school.
• Drinking sugary drinks is bad for your health as a whole.
• There is an association between socioeconomic status and access to quality healthcare services in urban neighborhoods.

Functions Of Hypothesis

The research issue can be understood better with the help of a hypothesis, which is why developing one is crucial. The following are some of the specific roles that a hypothesis plays: (Rashid, Apr 20, 2022)

• A hypothesis gives a study a point of concentration. It enlightens us as to the specific characteristics of a study subject we need to look into.
• It instructs us on what data to acquire as well as what data we should not collect, giving the study a focal point .
• The development of a hypothesis improves objectivity since it enables the establishment of a focal point.
• A hypothesis makes it possible for us to contribute to the development of the theory. Because of this, we are in a position to definitively determine what is true and what is untrue .

How will Hypothesis help in the Scientific Method?

• The scientific method begins with observation and inquiry about the natural world when formulating research questions. Researchers can refine their observations and queries into specific, testable research questions with the aid of hypothesis. They provide an investigation with a focused starting point.
• Hypothesis generate specific predictions regarding the expected outcomes of experiments or observations. These forecasts are founded on the researcher’s current knowledge of the subject. They elucidate what researchers anticipate observing if the hypothesis is true.
• Hypothesis direct the design of experiments and data collection techniques. Researchers can use them to determine which variables to measure or manipulate, which data to obtain, and how to conduct systematic and controlled research.
• Following the formulation of a hypothesis and the design of an experiment, researchers collect data through observation, measurement, or experimentation. The collected data is used to verify the hypothesis’s predictions.
• Hypothesis establish the criteria for evaluating experiment results. The observed data are compared to the predictions generated by the hypothesis. This analysis helps determine whether empirical evidence supports or refutes the hypothesis.
• The results of experiments or observations are used to derive conclusions regarding the hypothesis. If the data support the predictions, then the hypothesis is supported. If this is not the case, the hypothesis may be revised or rejected, leading to the formulation of new queries and hypothesis.
• The scientific approach is iterative, resulting in new hypothesis and research issues from previous trials. This cycle of hypothesis generation, testing, and refining drives scientific progress.

Importance Of Hypothesis

• Hypothesis are testable statements that enable scientists to determine if their predictions are accurate. This assessment is essential to the scientific method, which is based on empirical evidence.
• Hypothesis serve as the foundation for designing experiments or data collection techniques. They can be used by researchers to develop protocols and procedures that will produce meaningful results.
• Hypothesis hold scientists accountable for their assertions. They establish expectations for what the research should reveal and enable others to assess the validity of the findings.
• Hypothesis aid in identifying the most important variables of a study. The variables can then be measured, manipulated, or analyzed to determine their relationships.
• Hypothesis assist researchers in allocating their resources efficiently. They ensure that time, money, and effort are spent investigating specific concerns, as opposed to exploring random concepts.
• Testing hypothesis contribute to the scientific body of knowledge. Whether or not a hypothesis is supported, the results contribute to our understanding of a phenomenon.
• Hypothesis can result in the creation of theories. When supported by substantive evidence, hypothesis can serve as the foundation for larger theoretical frameworks that explain complex phenomena.
• Beyond scientific research, hypothesis play a role in the solution of problems in a variety of domains. They enable professionals to make educated assumptions about the causes of problems and to devise solutions.

Research Hypotheses: Did you know that a hypothesis refers to an educated guess or prediction about the outcome of a research study?

It’s like a roadmap guiding researchers towards their destination of knowledge. Just like a compass points north, a well-crafted hypothesis points the way to valuable discoveries in the world of science and inquiry.

Choose the best answer. 

Send Your Results (Optional)

Further reading.

• RNA-DNA World Hypothesis
• BYJU’S. (2023). Hypothesis. Retrieved 01 Septermber 2023, from https://byjus.com/physics/hypothesis/#sources-of-hypothesis
• Collegedunia. (2023). Hypothesis. Retrieved 1 September 2023, from https://collegedunia.com/exams/hypothesis-science-articleid-7026#d
• Hussain, D. J. (2022). Hypothesis. Retrieved 01 September 2023, from https://mmhapu.ac.in/doc/eContent/Management/JamesHusain/Research%20Hypothesis%20-Meaning,%20Nature%20&%20Importance-Characteristics%20of%20Good%20%20Hypothesis%20Sem2.pdf
• Media, D. (2023). Hypothesis in the Scientific Method. Retrieved 01 September 2023, from https://www.verywellmind.com/what-is-a-hypothesis-2795239#toc-hypotheses-examples
• Rashid, M. H. A. (Apr 20, 2022). Research Methodology. Retrieved 01 September 2023, from https://limbd.org/hypothesis-definitions-functions-characteristics-types-errors-the-process-of-testing-a-hypothesis-hypotheses-in-qualitative-research/#:~:text=Functions%20of%20a%20Hypothesis%3A&text=Specifically%2C%20a%20hypothesis%20serves%20the,providing%20focus%20to%20the%20study.

©BiologyOnline.com. Content provided and moderated by Biology Online Editors.

Last updated on September 8th, 2023

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How to Write an AP® Biology Lab Report

Writing a good lab report starts with taking smart steps when you conduct the lab. You should take notes about your methods, keep careful track of your data, and think critically during the lab about what could have been improved or done differently. If you are allowed to, taking pictures of your experimental setup is a good idea to make sure you are accurate in your descriptions when you write your lab report for your AP® Biology class. If photos are not allowed, consider making sketches in your lab notebook of any complicated setups. Don’t wait too long after you perform the lab to write the lab report, so that the information is still fresh in your mind.

Individual teachers vary in their specific requirements for AP Biology lab report formats, so make sure you pay attention to the instructions your teacher gives you. If you have any questions or if there is something you don’t understand, ask your teacher! They are there to help you. After you write your lab report, it is important to read over it and check for spelling or grammatical errors, which are not acceptable in scientific writing. Note that, with the exception of the title and materials list, you should always use complete sentences in your lab report.

Below are some general guidelines on how to write an AP Biology lab report. With this goal in mind, a great lab report is both concise and descriptive and contains the following sections:

The title of your lab report should be as specific as possible (i.e., “Lab 1” is not a specific title). Oftentimes, you can follow the model of “ The Effect of X on Y .” For example, in an experiment where you tested different types of fertilizer and how well they made potato plants grow, a good title would be “The Effect of Fertilizer Type on Growth in Potato Plants.”

You don’t need to go into too much detail in the title; that’s what the other sections are for. As an example, “ The Effect of Organic and Synthetic Fertilizers on Growth in Eighteen Potato Plants ” is too much information. You should be as concise as possible while still giving your reader a good idea of what type of experiment you performed and what they should expect from the overall report.

Although not all teachers will require an abstract, this section is good practice for reading and writing real scientific articles. This section should give a brief summary (typically less than 100 words) of the entire experiment and analysis. You should cover what is being studied, your hypothesis, and a summary of the results. You should also include a concluding statement of the big takeaways from the experiment.

Introduction/Background

This section of your lab report should provide your reader with any background information they will need to understand your experiment. You should introduce the purpose of the experiment in this section of the lab report so that it is clear why the lab experiment was performed.

In this portion of your lab report, you will state your hypothesis, or testable statement. Your hypothesis is generally written in an “If…, then…” format (eg, “If organic fertilizer is better for plant growth than synthetic fertilizer, then potato plants will grow taller when exposed to organic fertilizer than when exposed to synthetic fertilizer”). You should include any reasoning that went into the formation of your hypothesis.

For example, if you hypothesize that organic fertilizer will result in better potato plant growth than synthetic fertilizer, why do you think that? Generally, you need to provide a brief definition of key terms you use in this section when they are introduced.

Materials and Methods

In this portion of your lab report, you will go into detail about the materials you used in your experiment and what steps you performed. Typically, this section involves a bulleted list of all materials used and their quantities. However, different teachers may have different preferences for how the materials you used are communicated in your lab report. Remember to include all materials you used; for example, don’t forget items such as soil and water in a plant growth experiment.

In addition to the materials list, you will detail each step you took to complete your experiment. The goal of writing this section in any scientific field is to make your results reproducible by other scientists, which would make your experiment accurate and valid in the eyes of the scientific community.

Employing meticulousness in writing this section is preparing you for what to expect in the real world of science. With this in mind, make sure you mention all the variables that were controlled, along with the independent and dependent variables. In addition, you should use the past tense when writing this section, as your materials and methods are a description of an experiment that you have already performed. For example, you would write, “the height of each potato plant was measured daily”, not “measure the height of each potato plant daily.”

The results you obtained during your experiment are displayed in this section of your lab report. Usually, this will be in the form of table(s) and/or graph(s), depending on your experiment. Think about your experiment and results, and how you can best depict them visually.

When creating tables and graphs, make sure each one is clear and easy to follow and that they each have a descriptive title. Consider whether you should include averages for experiments in which multiple trials were performed. When you display numerical figures, units should always be included. If your lab report contains a graph, make sure to label both the X and Y axes appropriately and to include a key or legend if necessary. In some labs, you will perform statistical analyses; make sure to include this here if it was part of your experiment.

The statistical analyses, graphing tasks, and tabular data production required for your AP Biology lab report are directly tied to the science practices you will be tested on during the AP Biology exam, as shown in our AP Biology Study Guide and Materials article. So make sure you put your best effort into learning and mastering the skill set of representing scientific data in a visual manner and using statistics-based reasoning.

Often, results that do not support your hypothesis are just as valuable as results that do. Results that do not support your hypothesis do not mean that your experiment has “failed” or that you should make up false results. So, for this section of the lab report, it is extremely important that you always represent the actual data you obtained in the experiment.

Analysis and Discussion

This section is the real meat of your lab report. Here you will present an analysis of the results you obtained in your experiment and whether they do or do not support your hypothesis. Note that this is the terminology that should be used when discussing your hypothesis in light of your results (not “prove” or “disprove”). Remember, results that do not support your hypothesis are not invalid, and this is your chance to explain why you think these unexpected results occurred.

This portion of your lab report is also an opportunity to discuss any shortcomings of the experiment, materials, or methods, and a place to provide suggestions for things that could be improved if the experiment was performed again. Additionally, you may suggest related investigations that could be performed given the results of your experiment (e.g., testing different brands of organic fertilizer on potato plant growth if a fertilizer you initially used did not work as well as you expected).

You should strive to clearly explain the meaning behind your results and any implications these results have on the information discussed in your introduction/background section. You should reference your results in any statements you make about your experiment, either by quoting data directly (e.g., “the plants grew an average of 4.5 cm taller”) or by referencing the figure, table, or graph number (e.g., “As shown in Table 1, organic fertilizer produced greater average plant growth than synthetic fertilizer”).

In some cases, your teacher may provide a list of questions that should be answered in this section. If this is the case, remember to reference this list and make sure all questions have been addressed in your text. These questions can also potentially serve as a useful way to organize your analysis and discussion.

Sometimes, a concluding sentence or two is written at the end of the previous section (Analysis and Discussion), and sometimes it is given its own section. Either way, you will summarize your big takeaways from the experiment (what you were testing and whether your results support your hypothesis or not). This is usually the section of your AP Biology lab report that makes you think a lot about the big picture of your experiment.

Works Cited

In this final section of your lab report, you will list all the sources you used to create your lab report. At the minimum, this should include your provided lab manual and textbook. If you used any other books or online sources, make sure to list them here as well. Your teacher will likely provide you with the preferred lab report format for this section, but if not, American Psychological Association Style (APA format) is what you should use.

This section is a good reminder that you can absolutely use outside reliable sources for inspiration and information, but your lab report should always be in your own words and should never contain any plagiarized material.

Now you have learned key tips on how to write an AP Biology lab report in the best manner possible. As you go through your AP Biology class, you will have plenty of opportunities to create AP Biology lab report examples in the format your teacher asks for. To maximize your learning experience, try taking some AP Biology practice questions in the unit you are covering in class. It will help you pair all the scientific reasoning you did in the lab with the content tested for that unit of the AP Biology exam!

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Lab Report Template

Title : * a brief, concise, yet descriptive title

Example: "Types of Invertebrates Found in Pond Water"

Introduction: (State the problem or question to be answered)

* What question(s) are you trying to answer? * Not all experiments start with a question, some start with an observation and questions develop from further observations * Include any preliminary observations or background information about the subject Example: How many different types of insects are found in pond water? Does the location of the pond change the types of insects that live there? Does water quality affect the number of organisms?

Hypothesis:

* Write a possible solution for the problem or an explanation for the observation * Make sure this possible solution is a complete sentence. * Make sure the statement is testable, you may also include a null hypothesis . Example: Ponds located near populated areas will have less organisms than ponds found in isolated areas.

Materials and Methods:

*Make a list of ALL items used in the lab. Alternatively, materials can be included as part of the procedure. Example: Pond water, strainers, microscopes, field guides, petri dishes *Write a paragraph (complete sentences) which explains what you did in the lab as a short summary. Include the dependent and independent variables. Example: Water was sampled from each pond and examined under the microscope. A field guide was used to identify the types of organisms found and estimations of numbers were recorded. The manipulated variable is the pond location, the responding variable is the number of organisms.

Results (Data):

* This section should include any data tables, observations, or other information collected during the procedure. * Organize data onto tables and charts. * Graphs and charts should be labeled appropriately (X and Y axis) * Do not explain of make inferences at this points.

Conclusions:

* Accept or reject your hypothesis. * EXPLAIN why you accepted or rejected your hypothesis using data from the lab. * Include a summary of the data - averages, highest, lowest..etc to help the reader understand your results. Try not to copy your data here, you should summarize and reference KEY information. * List one thing you learned and describe how it applies to a real-life situation. *Discuss possible errors that could have occurred in the collection of the data (experimental errors) and suggest ways the experiment could be improved.

Other Resources on Lab Reports

Lab Report Rubric

Use Infographics for Lab Reports

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Genetics and Statistical Analysis

Once you have performed an experiment, how can you tell if your results are significant? For example, say that you are performing a genetic cross in which you know the genotypes of the parents. In this situation, you might hypothesize that the cross will result in a certain ratio of phenotypes in the offspring . But what if your observed results do not exactly match your expectations? How can you tell whether this deviation was due to chance? The key to answering these questions is the use of statistics , which allows you to determine whether your data are consistent with your hypothesis.

Forming and Testing a Hypothesis

The first thing any scientist does before performing an experiment is to form a hypothesis about the experiment's outcome. This often takes the form of a null hypothesis , which is a statistical hypothesis that states there will be no difference between observed and expected data. The null hypothesis is proposed by a scientist before completing an experiment, and it can be either supported by data or disproved in favor of an alternate hypothesis.

Let's consider some examples of the use of the null hypothesis in a genetics experiment. Remember that Mendelian inheritance deals with traits that show discontinuous variation, which means that the phenotypes fall into distinct categories. As a consequence, in a Mendelian genetic cross, the null hypothesis is usually an extrinsic hypothesis ; in other words, the expected proportions can be predicted and calculated before the experiment starts. Then an experiment can be designed to determine whether the data confirm or reject the hypothesis. On the other hand, in another experiment, you might hypothesize that two genes are linked. This is called an intrinsic hypothesis , which is a hypothesis in which the expected proportions are calculated after the experiment is done using some information from the experimental data (McDonald, 2008).

How Math Merged with Biology

But how did mathematics and genetics come to be linked through the use of hypotheses and statistical analysis? The key figure in this process was Karl Pearson, a turn-of-the-century mathematician who was fascinated with biology. When asked what his first memory was, Pearson responded by saying, "Well, I do not know how old I was, but I was sitting in a high chair and I was sucking my thumb. Someone told me to stop sucking it and said that if I did so, the thumb would wither away. I put my two thumbs together and looked at them a long time. ‘They look alike to me,' I said to myself, ‘I can't see that the thumb I suck is any smaller than the other. I wonder if she could be lying to me'" (Walker, 1958). As this anecdote illustrates, Pearson was perhaps born to be a scientist. He was a sharp observer and intent on interpreting his own data. During his career, Pearson developed statistical theories and applied them to the exploration of biological data. His innovations were not well received, however, and he faced an arduous struggle in convincing other scientists to accept the idea that mathematics should be applied to biology. For instance, during Pearson's time, the Royal Society, which is the United Kingdom's academy of science, would accept papers that concerned either mathematics or biology, but it refused to accept papers than concerned both subjects (Walker, 1958). In response, Pearson, along with Francis Galton and W. F. R. Weldon, founded a new journal called Biometrika in 1901 to promote the statistical analysis of data on heredity. Pearson's persistence paid off. Today, statistical tests are essential for examining biological data.

Pearson's Chi-Square Test for Goodness-of-Fit

One of Pearson's most significant achievements occurred in 1900, when he developed a statistical test called Pearson's chi-square (Χ 2 ) test, also known as the chi-square test for goodness-of-fit (Pearson, 1900). Pearson's chi-square test is used to examine the role of chance in producing deviations between observed and expected values. The test depends on an extrinsic hypothesis, because it requires theoretical expected values to be calculated. The test indicates the probability that chance alone produced the deviation between the expected and the observed values (Pierce, 2005). When the probability calculated from Pearson's chi-square test is high, it is assumed that chance alone produced the difference. Conversely, when the probability is low, it is assumed that a significant factor other than chance produced the deviation.

In 1912, J. Arthur Harris applied Pearson's chi-square test to examine Mendelian ratios (Harris, 1912). It is important to note that when Gregor Mendel studied inheritance, he did not use statistics, and neither did Bateson, Saunders, Punnett, and Morgan during their experiments that discovered genetic linkage . Thus, until Pearson's statistical tests were applied to biological data, scientists judged the goodness of fit between theoretical and observed experimental results simply by inspecting the data and drawing conclusions (Harris, 1912). Although this method can work perfectly if one's data exactly matches one's predictions, scientific experiments often have variability associated with them, and this makes statistical tests very useful.

The chi-square value is calculated using the following formula:

Using this formula, the difference between the observed and expected frequencies is calculated for each experimental outcome category. The difference is then squared and divided by the expected frequency . Finally, the chi-square values for each outcome are summed together, as represented by the summation sign (Σ).

Pearson's chi-square test works well with genetic data as long as there are enough expected values in each group. In the case of small samples (less than 10 in any category) that have 1 degree of freedom, the test is not reliable. (Degrees of freedom, or df, will be explained in full later in this article.) However, in such cases, the test can be corrected by using the Yates correction for continuity, which reduces the absolute value of each difference between observed and expected frequencies by 0.5 before squaring. Additionally, it is important to remember that the chi-square test can only be applied to numbers of progeny , not to proportions or percentages.

Now that you know the rules for using the test, it's time to consider an example of how to calculate Pearson's chi-square. Recall that when Mendel crossed his pea plants, he learned that tall (T) was dominant to short (t). You want to confirm that this is correct, so you start by formulating the following null hypothesis: In a cross between two heterozygote (Tt) plants, the offspring should occur in a 3:1 ratio of tall plants to short plants. Next, you cross the plants, and after the cross, you measure the characteristics of 400 offspring. You note that there are 305 tall pea plants and 95 short pea plants; these are your observed values. Meanwhile, you expect that there will be 300 tall plants and 100 short plants from the Mendelian ratio.

You are now ready to perform statistical analysis of your results, but first, you have to choose a critical value at which to reject your null hypothesis. You opt for a critical value probability of 0.01 (1%) that the deviation between the observed and expected values is due to chance. This means that if the probability is less than 0.01, then the deviation is significant and not due to chance, and you will reject your null hypothesis. However, if the deviation is greater than 0.01, then the deviation is not significant and you will not reject the null hypothesis.

So, should you reject your null hypothesis or not? Here's a summary of your observed and expected data: