IB Physics IA criteria explained

The Physics IA on the current course (first assessed in 2025) is marked out of 24 across four criteria worth 6 marks each. Here are our own plain-words summaries. We have not copied the IB's wording or descriptors, so use this page to understand the intent, and check the IB's official criteria, which your teacher can give you, for the exact version.

Total 24 marks, worth 20% of your grade. The IA takes about 10 hours and the report is capped at 3,000 words. The last two criteria are half the marks, so the thinking after the experiment is as important as the experiment.

Research design (6 marks)

What it rewards. A focused research question you wrote yourself, and a method that can really answer it. The relationship should be clear, the variables identified, the controls sensible and the amount of data enough to see a trend.

What moves an investigation up. Phrase the question so that the independent and dependent variables are obvious. Choose a range wide enough to show a trend with several values and repeats. Say why each control matters and how you will monitor it, and think about safety and ethics. Show that your method came from reasoning about the physics, not from a worksheet.

Common slips. A question that names a topic but no variables; five values squeezed into a narrow range; controls listed but not measured; no reasons given for choosing the apparatus; no background physics to support a prediction.

Checklist

• Can I name my independent and dependent variables in the question?
• Do I have at least five values, each repeated?
• Have I explained how I will keep each control constant?
• Is there a physics-based reason for the method?

Data analysis (6 marks)

What it rewards. Handling the raw data properly: recording it clearly, processing it correctly, carrying uncertainties through and presenting graphs that show what the data tells you.

What moves an investigation up. Record raw data with units and uncertainties. Process it step by step, with a worked example. Choose a graph that suits your relationship, add error bars, and use the gradient, intercept or a fit to extract a result with its uncertainty. Explain what the graph shows in words, so the reader does not have to guess.

Common slips. Uncertainty calculated once then ignored; graphs without error bars; a trendline forced through zero without a reason; rounding that hides real differences; processing with no explanation.

Checklist

• Does every raw value have units and an uncertainty?
• Have I shown a worked example of each calculation?
• Does my graph have axes, units and error bars?
• Does my result for the gradient or fit come with an uncertainty?

Conclusion (6 marks)

What it rewards. A clear answer to your research question, backed by your analysis and compared with accepted physics.

What moves an investigation up. State the answer in terms of your data: what the trend or value is and how certain you are. Compare your result with a theoretical or accepted value, and say whether the difference is within your uncertainty. Link your conclusion to the physics you introduced at the start and keep the claim to what the data supports.

Common slips. A conclusion that restates the method; claims beyond the data range; ignoring the uncertainty when comparing with theory; saying the "hypothesis was proved" from a single run; leaving out the accepted value.

Checklist

• Does my conclusion directly answer the question?
• Have I compared my result with accepted physics?
• Have I used my uncertainty when judging the agreement?
• Have I avoided claiming more than my data shows?

Evaluation (6 marks)

What it rewards. A realistic review of your method. It rewards naming specific weaknesses, showing how much they affected the result, and suggesting improvements that would actually help.

What moves an investigation up. Link each weakness to a visible effect in your data, such as scatter, an offset or a curve that departs from the prediction. Say which weaknesses mattered most and why. Propose specific improvements, such as a better timer, longer runs, or a different way of controlling a variable, and say how each would reduce a particular problem.

Common slips. "Human error" with no detail; a long list of problems with no ranking; improvements that are only "use better equipment"; ignoring weaknesses that are obvious in the graph.

Checklist

• Is each weakness specific and linked to my data?
• Have I said which ones mattered most?
• Does each improvement fix a named weakness?
• Have I suggested a realistic extension of the investigation?

Putting it together

Half the marks come from after the experiment, so leave enough time to process the data and evaluate, rather than spending all of your 10 hours collecting. If you are working in a group, remember that each student changes a different independent or dependent variable, uses unique data and writes an individual report.

For a question to investigate, see 30 Physics IA research questions. The Physics IA guide has the overview. If you are also planning an essay, Extended Essay criteria explained shows how a different kind of project is marked.

Written by Ejaz Ahmad, IB teacher since 2015. Checked against the IB's published guide, October 2026. Photon Resources is independent of the IB.