Lab reports are the backbone of science writing at every level. The format looks simple — title, abstract, introduction, methods, results, discussion — but knowing exactly what goes in each section, and what doesn't, is what separates a top grade from a pass.
The IMRAD Structure
Most scientific lab reports follow the IMRAD format: Introduction, Methods, Results, and Discussion. Some also include an Abstract (before the Introduction) and a Conclusion (after the Discussion). Here's what each section requires:
Title
Informative, not clever. Should tell the reader what the experiment investigated, ideally including the variables involved. "Effect of temperature on enzyme activity in liver extract" is better than "The Enzyme Experiment."
Abstract
150–300 words summarising the purpose, method, key results, and conclusions. Write this last. Include specific numerical results — don't just say "results were significant."
Introduction
Background theory, hypothesis, and rationale. Explain the scientific concept being tested and why this experiment is a valid way to test it. State your hypothesis clearly (if/then format or null/alternative hypothesis format).
Materials and Methods
Detailed enough that another scientist could exactly replicate your experiment. Write in past tense, passive voice. Include: materials and concentrations, sample sizes, controls, measurements taken, and any safety precautions.
Results
Present your data without interpretation. Use tables and graphs (properly labelled). Describe trends in text but don't explain them here — that's what the Discussion is for. Include statistical test results (mean, SD, t-test outcomes, etc.).
Discussion
Interpret your results. Did the results support your hypothesis? How do they compare to published literature? What were the sources of error and how did they affect validity? What would you change in a repeat experiment?
Conclusion
Brief (one paragraph) — directly answers your research question and states whether your hypothesis was supported. Some instructors omit this and end with the Discussion; check your instructions.
Passive Voice and Tense
Science writing has specific conventions for voice and tense that differ from other academic writing:
- Methods section — past tense, passive voice. "The samples were incubated at 37°C for 30 minutes." (Not: "We incubated the samples.")
- Results section — past tense for what you observed; present tense for tables and figures. "Figure 1 shows a positive correlation between temperature and reaction rate."
- Introduction and Discussion — present tense for established scientific facts; past tense for what previous studies found.
Figures, Tables, and Data Presentation
- Every figure and table must have a number and a descriptive caption (Figure 1, Table 2, etc.)
- Figure captions go below the figure; table captions go above the table
- Axis labels on graphs must include the variable name and units (e.g., "Temperature (°C)")
- Include error bars on graphs where appropriate (standard deviation or standard error)
- Every figure and table must be referred to in the text ("as shown in Figure 1...")
Writing a Strong Discussion
The Discussion is worth the most marks in many lab reports and is the most frequently underwritten section. It should:
- Address each element of your hypothesis directly — was it supported or refuted by your results?
- Explain your results in terms of the underlying science — why did you observe what you observed?
- Compare your results to published data — agree? Disagree? Why might they differ?
- Identify sources of error honestly — random error (measurement variability) and systematic error (consistent bias in your methodology)
- Suggest improvements for future experiments that would address the limitations you've identified
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