Introductory Biology at

Writing a Lab Report


This material appears in your lab manual.


A considerable part of your lab grade is determined by your lab report. Your instructor may give you more specific guidelines for writing your paper.

You can get help with the clarity and correctness of your lab report at:

The Writing Center
101 McIver Bldg.
Mon.-Thurs. 9 AM to 8 PM
Fri. 9 AM to 3 PM

Don't ask them to help you with the science. If you need help understanding the experiment you should go to the Tutoring Room or see your lab instructor.


Science is a process that depends heavily on an exchange of information. Your lab report will be written in the same format that professional scientists use to report their research. Scientific writing is brief, concise, and specific. You can write an excellent report that includes all the necessary details in about 4 or 5 pages. Before you write your first draft, make sure you understand the experiment.

Every lab report includes each of the following parts:


Strategies For Starting the Report

Know your audience. Write this report so it can be read by a UNCG freshman who has not taken Introductory Biology. That means you must explain what you did, and why, in terms that a typical high school graduate can understand. Define any scientific terminology you use. Don’t assume your reader has read the lab manual or been to your class. Tell them what they need to know to understand your report. Provide enough detail that they could do their experiment, but eliminate unnecessary details.

Try these steps to build your report:

  1. Write out your hypothesis.
  2. Write out your methods (in your OWN WORDS, citing the lab manual as your source).
  3. Graph your results.
  4. Write a BRIEF description of your results (use complete sentences).
  5. Write a 1 - 2 sentence evaluation of your hypothesis (do the data support it, or do you reject it?).

Understanding Your Experiment

The hardest part of understanding your experiment is knowing

  • What hypothesis you tested.
  • What the variables were.
  • Whether your data support your hypothesis.

A hypothesis is a statement that can be tested by conducting an experiment or collecting data. A hypothesis is sometimes described as an "educated guess", but it is really a specific prediction. A hypothesis can be proven false, but it is NEVER PROVEN TRUE!

For example, suppose you want to study the effect of staying up late at night to cram for an exam. Does it help your grade, or hurt it? A simple hypothesis might be:

"The amount of sleep a student gets the night before an exam will affect her score on the exam."

But scientists always try to make their hypotheses as specific as they can. So, a better hypothesis would be:

"The more sleep a student gets the night before an exam, the higher her score will be."

This statement is testable. All we need are some good data on student sleep patterns and exam scores. We could test this hypothesis by performing an experiment, but it might be tough to find students who would be willing to risk making bad grades just to test our hypothesis. So instead, we can use a survey to collect the data, and see if the data support our hypothesis or refute it.

A good hypothesis deals with the relationship between two variables. In this case, one variable is the amount of sleep a student gets, and one is the student’s grade on the exam. These two variables are expected to have a clear cause-and-effect relationship. We suspect that a lack of sleep will CAUSE the student's grade to be low. We call the grade the dependent variable because it DEPENDS on how much sleep a student gets. In any experiment, the scientist manipulates one variable to see how it affects the other variable. The one that the scientist manipulates is the independent variable, which causes changes in the dependent variable. When you look at a hypothesis, you should be able to quickly figure out which variable is independent and which is dependent.


Title

Your title should be about 8 to 12 words long, and it should mention both the independent and dependent variables.

A bad title: "Exam Grades"
A weak title: "Sleep vs. Exam Grades"
A strong title: "Amount of Sleep Affects Student Performance on Biology Exams" (Notice that both the independent variable [amount of sleep] and the dependent variable [exam score] are mentioned. It is clear that the grade depends on the amount of sleep).

Introduction

The purpose of the Introduction section is to set the stage for your hypothesis. Your introduction should begin with background information that is general. Imagine that you are writing your introduction for a friend who has never had college biology. Give a clear explanation of what your study is all about, defining any specialized terms you use. Organize your introduction carefully; start off very broad, and then narrow down what you are talking about.

For example, if you are writing about the effects of sleep on exam performance, you should start with the basics: why people need sleep, what happens during sleep, and what are some known results of a lack of sleep.

In this part of the paper you will want to use information from various sources that you research in the library, and cite the sources correctly. Then, narrow down your introduction to the specific hypothesis you tested.

Methods

Your Methods section is pretty easy to write if you are careful about a couple of things:

  • Include enough detail so that your reader could repeat your experiment and test your hypothesis.
  • Eliminate the unnecessary details. Your reader doesn't need to know everything you did, just enough to do the experiment. Ask yourself, "If I leave this out, will my reader be able to do the experiment and get the same results I did?" If so, then leave it out!
  • DO NOT copy the methods from the lab manual. That is a big mistake! Write the methods in your own words.
  • Keep it short and sweet. After you write the first draft of the methods, go back and look for ways to shorten it. Eliminate the unnecessary details.

Results

The Results section has two elements: a textual description of your results, and a graphical summary of your results.

  • Text

    The text should describe the pattern or trends seen in your data. It should be short, but should give your reader a mental picture of what your results show. The results should be so complete and clear that the reader doesn't have to look at your graph to get a clear picture of what the data show.

    For example:

    "The data from my survey show that students who get very little sleep before exams generally make grades less than 70%. Students who sleep less than 3 hours do not benefit greatly, but students who sleep 6 or more hours improve their exam scores by 15% on average. In general, the more sleep a students gets before the exam, the better their exam grade will be. The pattern is the same in Biology 111 and 112. Students in Biology 112 generally score higher than students in Biology 111."

    Notice that the Results section describes the general pattern, but it does not list every data point. The data points are represented in graphs and tables.

  • Graphs

    Your instructor will require you to graph your results. You are not required to use a computer, but you must use graph paper or a ruler to produce neat, accurate graphs. Colors are nice, but not required. Neatness counts!

A good graph has:

  • The independent variable on the x-axis (horizontal axis)
  • The dependent variable on the y-axis (vertical axis)
  • Each axis labeled with the name of the variable and the units of measure
  • Different colors or symbol shapes for different data sets
  • Axes that are scaled appropriately
  • A descriptive caption

Here is an example of a good graph (DO NOT add the labels shown in red; they are there just helpful notes):

Discussion

The Discussion section is the hardest one to write, but it is the most important. You can’t write a good discussion until you have the rest of your report in good shape. Make sure your discussion answers all the following questions:

  • Was your hypothesis supported, or did you reject it?
  • How do your data compare to the data collected by other students in the class? Were your results close to the average or very different? Why?
  • Why did you get the results you did? What principles of biology or biological processes explain what happened?
  • Did all students in the class test the same hypothesis? If not, what other hypotheses were tested? What were the results? How do these experiments fit with your experiment?
  • What is the significance of this work?
  • What experiment should be done next? (Science never ends). Can you think of ways to do this experiment over and get better results? Or can you think of other experiments that should be done? What hypotheses would you test next?

Literature Cited

In your Literature Cited section, you must list every source you used in writing your report. The correct, general format is:

Author, date, title, publication information.

Some examples include:

(from a paper in a journal):

Somnolent, I.M. 1996. College student performance improves with increased sleep time. Journal of Sleep Behaviors 35:111-117.

(from a chapter in a book):

Repose, D. and S. Slumber. 1992. Sleep Patterns, Pp. 22-39 in Principles of Sleep, D. Repose et al, eds. San Francisco: Siesta Publishers.


Other Tips:

  • You should use the past tense and personal pronouns instead of passive voice.

Poor: "Three hours was the amount of time the subject slept."

Better: "Subjects slept for 3 hrs."

  • Units of measurement (metric) are abbreviated and numbers are not spelled out (unless they start sentences).
  • While you should use materials such as textbooks, notes, or the lab manual in preparing the report, do not quote these sources directly. You must cite any sources used by listing them in the Literature Cited section at the end of the report.
  • You must acknowledge the original ideas of others, no matter which section of the paper those ideas are conveyed. Give the source in the sentence or at the end of the sentence in which you mention another person’s information or idea. An example:

College students, particularly freshmen, believe that they need less than 6 hours of sleep each night to maintain success (Repose, 1992).

  • Work in shifts to write several drafts. Try to shorten subsequent drafts by deleting any non-informative words, phrases, and sentences.

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