Writing a Lab Report

Remember: The expectations for a lab report will vary from TA to TA. When in doubt about anything, consult the lab manual or rubric(s), or email the TA!

Information in this guide has been adapted from Writing in Biology by Karin Knisley, and “The Lab Report” from the University of Toronto.

An abstract is a short paragraph (< 200 words) that summarizes the experiment’s purpose, major findings, significance, and the conclusion.

• The abstract may also contain a sentence about theory or experimental methods.
• The abstract is written in past tense.
• Most undergraduate lab reports do not require an abstract.

The introduction details background information about concepts or theories and provides the hypothesis and predictions for the experiment.

• Background:
  • Reverse triangle format: Start broad, then focus in on information more relevant to the hypothesis/this experiment.
  • Either summarizes background information from the lab manual or compiles relevant information from outside sources to be cited in APA style.
  • May also contain information about why the experiment is important. Will it prove a new theory? Is it economically important?
  • Written in present tense.
• Hypothesis: The hypothesis is written in past tense and should use specific wording.
• Predictions: The predictions are also written in past tense and detail what specific experimental outcomes were expected.

For example: “It was hypothesized that fertilizer would have a positive impact on the health of Pisum sativum. It was predicted that the plants that received fertilizer would have a higher chlorophyll concentration than those that did not receive fertilizer, which would indicate healthier plants.”

The methods section details the experimental procedure from the lab.

• Typically in paragraph format, though some TAs may accept a bulleted list.
• Should not copy directly from the lab manual.
• Any changes to the lab procedure or deviations from the procedure in the manual made during the experiment should be noted.
• Written in passive past tense. This removes the experimenter from the experiment and ensures the procedure reads as something that was already done, rather than something to be done.
  • Correct: “Acid was added to the test tube.”
  • Incorrect: “I added acid to the test tube,” or, “Next, add acid to the test tube.” 
• There should be enough detail for another scientist to replicate the experiment. However, superfluous details, such as sterilizing a workbench, should be omitted.
  • For more examples of superfluous details, see Chapter 5 of Writing in Biology (page 86).
  • Generally speaking, if you knew to do it prior to doing the experiment, your reader will know to do it too – assume the audience is familiar with labs.

The results section consists of two parts: A series of graphs and figures, and paragraph(s) explaining those graphs and figures in words.

• The paragraphs should be written in past tense. Specific figures/tables should be referenced, and the most relevant data should be highlighted.
• The data should be summarized, not interpreted. Interpretation is saved for the discussion/conclusion section.

This section of a lab report consists of four or five major parts, as follows. It generally follows a triangle format:

• Whether or not the hypothesis was supported.
  • Typically the first sentence of the discussion. 
• Why the hypothesis was (not) supported.
  • References specific data from the experiment to support why (or why not) the hypothesis was supported.
    • Good: "It was proven that fertilizer helps peas grow taller. Plants given fertilizer grew an average of 10cm taller than those not given fertilizer." 
    • Not as good: "It was proven that fertilizer helps peas grow. Plants given fertilizer were taller than those not given fertilizer."
  • Some TAs may ask that this reasoning is then related to other scientific literature.
    • Do the findings from this experiment support findings from other experiments?
• Sources of error that impacted the results, and what could be done to fix those errors.
  • For potential sources of error, see chapter 5 of Writing in Biology (page 108).
• Suggestions for future experiments.

• Citations and formatting should be done in APA format unless otherwise specified by the TA.
  • Therefore, findings from other scientific papers will often be paraphrased, not directly quoted.
• Information accepted as true within the discipline is to be written in present tense.
• Information about the experiment is not widely accepted as true and should be written about in past tense. 
• When in doubt, consult the lab manual, syllabus, or rubric, or ask the TA.
• Generally, the tone of a lab report is formal. Literary devices, rhetorical questions, first-person-POV, and personal pronouns are discouraged.
  • This is done to reduce bias and promote subjectivity. A scientist's opinions have no place in the experiment. 
• Assume the audience has some familiarity with scientific methods and jargon but explain any complex concepts relevant to the experiment.
• Binomial species names may be italicized and may be abbreviated after one use:
  • For example, after the first use of Alces alces, it can be written as A. alces.

Remember: When in doubt, ASK THE TA! Specific requirements for lab reports change from TA to TA, even for the same class! This is meant to serve as a very general guide for what can be a very variable genre of writing.