What a lab report is for
A lab report is the scientific community's standard way of sharing an investigation. Its purpose is reproducibility and scrutiny: a reader should understand what you asked, exactly how you tested it, what you found, and what it means — in enough detail to repeat the work. Because the goal is clarity rather than originality of expression, lab reports follow a predictable structure, and learning that structure is most of the task.
The standard sections
Most lab reports follow a fixed order, closely related to the IMRaD structure used in research papers:
| Section | Answers |
|---|---|
| Title & abstract | What was investigated, and a brief summary of the whole report. |
| Introduction | The background, the aim, and the hypothesis. |
| Methods (Materials & Methods) | Exactly how the experiment was carried out. |
| Results | What was found — data, tables and figures, no interpretation. |
| Discussion | What the results mean, and whether they support the hypothesis. |
| Conclusion & references | The key finding, and the sources cited. |
Introduction, aim and hypothesis
The introduction gives just enough background theory to frame the experiment, then states the aim (what you set out to investigate) and the hypothesis (your testable prediction). Keep the theory focused on what the reader needs to understand your specific experiment — a lab report is not a textbook chapter. A clear, falsifiable hypothesis is essential, because the discussion will return to it directly.
Methods — past tense, passive voice
The methods section is where lab reports differ most from essays. Write it in the past tense and usually the passive voice ("the solution was heated to 60°C"), describing what was done rather than instructing the reader to do it. Give enough detail for replication — quantities, equipment, conditions, procedure — but do not turn it into a numbered recipe unless your course requires it. The test is simple: could a competent peer reproduce your experiment from this section alone?
Write "10 mL of hydrochloric acid was added to the flask," not "Add 10 mL of hydrochloric acid to the flask." A report records what happened in the past; it does not give the reader instructions.
Results — data without interpretation
The results section presents your findings clearly and objectively. Use tables and graphs to show patterns, label and number every figure, refer to each in the text, and state what the data show — but save the meaning for the discussion. Include relevant calculations and, where appropriate, an estimate of uncertainty or error. The discipline here is restraint: report what you observed, including results that did not match your prediction, without yet explaining them.
Discussion and conclusion
The discussion is where the marks concentrate. Interpret your results: do they support the hypothesis? How do they compare to expected or published values? What sources of error might explain any discrepancy, and how could the method be improved? Be honest about limitations — acknowledging error shows scientific maturity, not weakness. The conclusion then states the key finding concisely, answering the aim. Cite any theory or published data you draw on in your required style; our Vancouver and APA guides cover the styles most science courses use.
Common mistakes to avoid
- Writing methods as instructions ("add the acid") instead of past-tense description.
- Interpreting results in the results section instead of the discussion.
- Figures and tables that are unlabelled or never referred to in the text.
- Hiding unexpected results or ignoring sources of error.
- A discussion that restates the results without explaining what they mean.
Frequently asked questions
What tense should a lab report be written in?
The methods and results are written in the past tense because they describe what was already done and found. The introduction and discussion can use present tense for established facts and general scientific principles.
Should I use the passive voice in a lab report?
The methods section is traditionally written in the passive voice ("the sample was heated") to keep the focus on the procedure rather than the experimenter. Some courses now accept active voice, so check your guidelines.
Where do I interpret my results?
In the discussion, not the results section. The results section presents the data objectively, and the discussion explains what they mean, whether they support the hypothesis, and what might account for any error.