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24 marks across 4 criteria, each worth 6 marks. Weighting: 20% of the final IB Biology grade (Both HL and SL (shared IA)).
Addresses how clearly the research question is framed, how well the methodology is justified, and whether the variables and controls are appropriate.
| Band | Descriptor summary |
|---|---|
| 1–2 marks (Basic) | Research question is vague. Methodology is listed but not justified. Few control variables identified. |
| 3–4 marks (Satisfactory) | Focused question with most variables identified. Method reproducible but justification is partial. |
| 5–6 marks (Excellent) | Precisely framed RQ with strong biological rationale. Fully justified method. All variables controlled with quantified tolerances. |
Covers accurate recording of raw data, appropriate processing (including uncertainty), and effective presentation.
| Band | Descriptor summary |
|---|---|
| 1–2 marks (Basic) | Raw data incomplete. Processing minimal. No uncertainties or statistics. |
| 3–4 marks (Satisfactory) | Data recorded with units and uncertainties. Basic processing (mean, SD). One figure. Statistical test present but assumptions not checked. |
| 5–6 marks (Excellent) | Data tables complete with uncertainties. Full worked example of each calculation. Justified statistical test with reported effect size. Effective, accurate figures. |
Assesses how the conclusion links processed data to the research question and to established biology — including comparison with accepted values or literature.
| Band | Descriptor summary |
|---|---|
| 1–2 marks (Basic) | States an answer without quantitative support or biological reasoning. |
| 3–4 marks (Satisfactory) | Answer supported by data trend. Biological mechanism explained. Limited comparison with literature. |
| 5–6 marks (Excellent) | Quantitative, mechanism-supported conclusion. Explicit comparison with literature. Residual data variance explicitly acknowledged. |
Evaluates methodological weaknesses, sources of error, and — critically — gives specific, realistic improvements.
| Band | Descriptor summary |
|---|---|
| 1–2 marks (Basic) | Generic limitations listed. No impact analysis. Vague improvements. |
| 3–4 marks (Satisfactory) | Specific weaknesses identified with some ranking. Improvements connected to weaknesses. One credible extension. |
| 5–6 marks (Excellent) | Weaknesses ranked by impact on the uncertainty of the conclusion. Random vs systematic errors distinguished. Specific, realistic improvements and coherent extension. |
The IB Biology IA is marked out of 24, with 4 criteria each worth 6 marks: Research Design, Data Analysis, Conclusion, and Evaluation. The IA contributes 20% of the final IB Biology grade at both HL and SL.
The 2025 rubric removed the standalone Communication criterion. Communication quality is now judged implicitly across the 4 remaining criteria. Conclusion and Evaluation together now account for 50% of IA marks (12/24), up from the previous weighting.
The descriptor for 5–6 marks requires the work to meet every expectation of the lower bands plus additional sophistication: quantitative trend statements, explicit comparison with literature, ranked weaknesses with impact analysis. A single missing sub-point typically caps a criterion at 4 marks.
Yes, both HL and SL Biology students submit the same IA format, graded against the same 4-criterion, 24-mark rubric. The depth of biological analysis expected in the Conclusion is calibrated to the student's level of syllabus engagement, but the rubric itself is identical.
The rubric rewards the correct statistical test for your data — not a specific one. Examiners expect you to justify your choice (e.g. t-test for two means, ANOVA for three or more, chi-squared for categorical counts, Pearson or Spearman for correlations) and verify its assumptions. An incorrect test applied well scores lower than a simpler correct test.
A Cerebrum IB Biology tutor will review your IA draft against all 4 criteria and give examiner-style feedback in 48 hours.
Book IA Review