how to write
a lab report

a lab report is not a diary of what you did. it is an argument: here is a question, here is the evidence, here is what the evidence supports. most lost marks come from mixing those jobs together, not from bad science.

start with the
structure your course wants

check the rubric or lab manual first. most reports follow the same order, and the rubric tells you how many marks sit in each part:

title · abstract · introduction · methods · results · discussion · conclusion · references

some courses merge or drop sections, so follow yours. when the rubric and this guide disagree, the rubric wins.

write the methods
and results first

you do not have to write in the order the report is read. the methods and results are the parts you know best, so do them first. the introduction and abstract are easier once you know what you found.

methods: what you did,
in past tense

describe the procedure so someone else could repeat it. list the materials, the steps in order, and anything you changed from the manual. use past tense and passive or plain active voice, whichever your course prefers. do not explain why the method works here. that belongs in the introduction.

results: what you found,
with no opinion

present the data and stop. use a table or graph for the main result and refer to it in a sentence: "figure 1 shows the rate of reaction at each temperature." a good figure has a number, a caption that stands alone, labelled axes and units. keep raw data in an appendix if your course asks for it.

do not say why the results came out that way yet. a results section that explains itself is a discussion in the wrong place.

discussion: what it means,
and how sure you are

this is where most of the marks are. answer four questions in order:

• what did the data show, in one sentence?
• does it support your hypothesis, and how do you know?
• what could have affected the result: measurement error, equipment limits, assumptions?
• what would you change or test next?

be specific about error. "human error" is not an explanation. "the stopwatch was started by hand, which adds about a few tenths of a second to each time" is. if your result does not match the expected value, say so and explain what might have caused the gap. do not adjust the data to fit.

introduction: the question
and why it matters

write this after the discussion. state the topic, the relevant theory in a few sentences, and the hypothesis or aim. keep it short. one idea per paragraph, and only include theory you use later.

abstract and conclusion

the abstract is a summary of the whole report in one paragraph: aim, method, main result, conclusion. write it last. the conclusion is two or three sentences that answer the original question. neither should contain anything new.

check before you hand in

• every table and figure is numbered, captioned and mentioned in the text.
• units and significant figures are consistent.
• the conclusion answers the question you asked in the introduction.
• sources are cited in the format your course requires.
• you read it aloud once. awkward sentences are easy to hear.

if the maths is the problem

a lot of lab report trouble is really data trouble: error, graphs, a calculation that gives a strange number. if that is where you are stuck, see statistics, chemistry or physics, and read asking a question that gets an answer before you post it. if your instructor can clarify the rubric, a short email before the deadline is worth it.

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