In QCE Biology, your three internal assessments (the data test, the student experiment and the research investigation) make up 50% of your final result. The 2025 subject report includes annotated student work showing exactly what high-scoring experiments and research investigations look like.
This guide breaks down the internal assessment sections of QCAA's 2025 Biology subject report. It covers how students scored on each IA, what strong responses did, and the changes under the revised 2025 syllabus that students completing Units 3 and 4 from 2026 need to know. For the external exam, see our companion 2025 QCE Biology external assessment breakdown.
Key Takeaways
- Internal assessments are worth 50% of your Biology result: data test (IA1) 10%, student experiment (IA2) 20%, research investigation (IA3) 20%.
- IA2 and IA3 marks were the most likely to be adjusted. QCAA agreed with schools' marks 89.04% of the time for IA2 and 90.60% for IA3, and changes were mostly downwards.
- The hardest criteria to get full marks in were Interpretation and evaluation (IA2) and Conclusion and evaluation (IA3). Only about a quarter of students got full marks in each.
- Strong experiments used the right statistics and graphs for the research question, found patterns in uncertainty and explained how each limitation weakened the evidence.
- Under the 2025 syllabus, improvements must address reliability and extensions must address validity, and cladistics and phylogeny have moved into Unit 4.
How Internal Assessment Works in QCE Biology
| Assessment | Type | Weighting | What You Do |
|---|---|---|---|
| IA1 | Data test | 10% | Answer short-response questions on 2–4 datasets under supervised conditions |
| IA2 | Student experiment | 20% | Modify a practical, collect primary data, analyse it and write a scientific report |
| IA3 | Research investigation | 20% | Evaluate a claim using secondary evidence from scientific sources |
| External assessment | Two examination papers | 50% | Units 3 and 4 |
Your school writes each IA, but before students sit it the QCAA must endorse it, checking that it matches the syllabus and is fair. After marking, the QCAA confirms a sample of student responses to check that your school's marks are accurate.
💡 New to the system? Read our explainer on how QCE internal assessments work.
How Students Scored in 2025
| Assessment | Maximum Mark | Approx. % on Full Marks |
|---|---|---|
| IA1 (data test) | 10 | 30% |
| IA2 (student experiment) | 20 | 16% |
| IA3 (research investigation) | 20 | 19% |
| Total IA | 50 | 8% |
Approximate values read from the mark distribution charts in QCAA's 2025 Biology subject report.
Full marks was the single most common result on every IA, but most students finished somewhere between 35 and 49 out of 50. The two 20% tasks, the experiment and the research investigation, are together worth four times as much as the data test, so that is where most marks are won or lost.
How Reliable Were School Marks?
| Assessment | Instruments Endorsed First Time | Samples Reviewed | Agreement With School Marks |
|---|---|---|---|
| IA1 | 40% | 3,487 | 100% |
| IA2 | 93% | 3,491 (+22 additional) | 89.04% |
| IA3 | 85% | 3,470 (+18 additional) | 90.60% |
Source: QCAA Biology subject report, 2025 cohort.
What this means for students:
- Your data test mark will stand. QCAA agreed with every school's IA1 marks.
- About 1 in 10 schools' IA2 and IA3 marks were changed, almost always downwards. In IA3, every change to the Conclusion and evaluation criterion (5.37% of samples) was a reduction.
- Only 40% of school data tests were endorsed the first time, mostly because questions did not align with the syllabus objectives. Your final data test has been checked, so expect it to follow the syllabus question specifications closely.
IA1: Data Test (10%)
The data test gives you two to four datasets, ideally based on practicals or case studies you completed in class, and a series of short-response questions that each assess a single objective.
What QCAA's Samples Show
- Show each step of a calculation. One full-mark sample calculated cell size as field of view ÷ number of cells (0.045 ÷ 2 = 0.0225 mm) and converted it to 22.5 µm, earning a mark for each step.
- Interpret statistics in words. A strong response explained that a Simpson's diversity index of 0.59 means the probability that two randomly chosen plants are the same species is 1 − 0.59 = 0.41 (41%).
- Follow-through marks are awarded when an earlier error affects a later answer but you still show the correct skill.
- Cut-offs are applied exactly. In one example, 14/23 = 60.9%, which is above the 60% cut-off, so it earned 7 out of 10.
- Answer the cognitive verb. A 2-mark infer question typically gives 1 mark for the conclusion and 1 mark for the reasoning.
What Changes for IA1 Under the 2025 Syllabus
- Perusal time is 5 minutes.
- The question specifications have been revised. For example, compare now aligns more closely with analysing evidence (similarities and differences).
- Cladistics and phylogeny have moved into Unit 4, so they may no longer appear in the Unit 3 data test.
- The Science inquiry subject matter now includes more practicals, which may give schools a wider range of datasets.
IA2: Student Experiment (20%)
The student experiment asks you to modify a practical, collect primary data, process and analyse it, and write a scientific report that answers your research question.
How Students Scored on Each Criterion
| Criterion | Marks | Approx. % on Full Marks | Most Common Mark |
|---|---|---|---|
| Research and planning | 6 | 33% | 5 |
| Analysis of evidence | 6 | 34% | 6 |
| Interpretation and evaluation | 6 | 26% | 4 |
| Communication | 2 | 81% | 2 |
Approximate values read from QCAA's 2025 criterion charts.
What Earned the Marks
Research and planning: QCAA's samples included a Unit 3 investigation into how distance from a walking path affected the abundance of flat-stemmed wattle. The student justified every modification, for example:
- reducing quadrat size from 10 × 10 m to 4 × 4 m so the data better reflected changes with distance (validity)
- increasing the number of transects from one to four to reduce the impact of outliers (reliability)
- shortening the transect from 70 m to 28 m because most change occurred close to the path (precision).
A strong rocky-shore experiment also showed considered risk management: a hazard table with controls, plus environmental and cultural considerations, such as acknowledging the Traditional Custodians and avoiding middens.
Analysis of evidence: Full marks needed processing that fit the research question. QCAA listed good matches, such as:
- scatterplots with correlation coefficients for relationships
- bar graphs or boxplots with error bars and t-tests for comparisons
- line graphs with error bars for trends
- standard deviation or standard error to show uncertainty.
Strong responses identified patterns in uncertainty, not just repeated standard error values. The wattle sample showed that removing outliers raised R² from 0.4919 to 0.9396 and explained what that meant for confidence in the trend.
Limitations had to explain how each one weakened the evidence, considering outliers, number of data points, spread, missing data and confounding factors.
Interpretation and evaluation: This was the hardest criterion. Strong responses:
- wrote a conclusion that answered every part of the research question with evidence, as in an arthropod sample that reported means, standard errors and p-values for each comparison
- discussed reliability and validity using specific evidence, such as percentage uncertainties and biased site selection
- suggested improvements and extensions that followed logically from the limitations, such as stratified sampling to cover every zone.
Communication: Full marks needed precise terminology (e.g. abundance, distribution, confounding factors), correct units and nomenclature (e.g. Rhizophora stylosa), labelled graphs with error bars identified, and a consistent referencing style such as APA or Harvard.
What Changes for IA2 Under the 2025 Syllabus
The criteria have been reorganised (for example, into Forming, Finding, and Interpreting and Evaluating), but the standards teachers apply are the same. Key expectations:
- a considered rationale that explains why the independent and dependent variables matter
- justified modifications that explain how each change improves reliability or validity
- a Unit 3 research question that clearly links to biodiversity or ecosystem dynamics, such as carrying capacity, population growth or species distribution
- improvements that address reliability and extensions that address validity.
IA3: Research Investigation (20%)
The research investigation asks you to evaluate a claim by developing a research question and analysing secondary evidence from credible scientific sources.
How Students Scored on Each Criterion
| Criterion | Marks | Approx. % on Full Marks | Most Common Mark |
|---|---|---|---|
| Research and planning | 6 | 52% | 6 |
| Analysis and interpretation | 6 | 36% | 6 |
| Conclusion and evaluation | 6 | 25% | 5 |
| Communication | 2 | 85% | 2 |
Approximate values read from QCAA's 2025 criterion charts.
What Earned the Marks
Research and planning: One strong sample evaluated the claim that genetic modification is a viable option for maintaining food production. The student narrowed the claim to Bt corn, explained how the Cry1Ab gene gives pest resistance, defined "maintaining food production" as crop yield, and developed a specific research question: "Does Bt corn produce a greater crop yield than conventional non-Bt corn?"
Analysis and interpretation: QCAA wants evidence that is directly relevant to the research question, presented clearly (for example, with referenced snips of key tables and graphs) and drawn from several sources, so that one source can corroborate another or cover its limitations. Limitations should be specific to the research question.
Conclusion and evaluation: This was the hardest IA3 criterion. Strong responses:
- discussed the quality of the evidence, for example noting that the Bt corn studies used single-year data and excluded 13% of surveys, which could introduce selection bias
- reached a justified conclusion while recognising the limits of the claim, such as only one crop and one outcome being studied
- suggested improvements and extensions relevant to the claim, such as multi-year data or other GM organisms
- extrapolated carefully. A gene therapy sample explained that results from mouse studies could not be directly applied to human patients.
What Changes for IA3 Under the 2025 Syllabus
- The task specifications now match the mid-level descriptors in the marking guide.
- The syllabus gives examples of credible sources students can use.
- Group elements have been added to some Forming and Finding activities.
- With cladistics and phylogeny now in Unit 4, claims about them can be used in research investigations.
💡 Get a clear picture of every cognitive verb with our complete guide to QCE cognitive verbs.
How to Improve Your Biology IA Results
- For the data test, show every calculation step and interpret statistics in words.
- Justify every modification to your experiment by saying whether it improves reliability or validity.
- Choose statistics and graphs that fit your research question, and always show uncertainty.
- Look for patterns in uncertainty and outliers, and explain what they mean for confidence in your results.
- Explain how each limitation weakens the evidence, not just what the limitation is.
- Answer every part of the research question in your conclusion, with evidence.
- Link improvements to reliability and extensions to validity.
- Use several credible sources in your research investigation, and evaluate their quality.
For more preparation:
- read our 2025 QCE Biology external assessment breakdown
- follow our guide to getting an A in QCE Biology
- learn how IA1, IA2 and IA3 work
- understand how the QCE ATAR is calculated.
Need Help With QCE Biology?
Our QCE Biology tutors work one-on-one with students to prepare for the data test, plan and analyse a high-scoring student experiment, and write a well-evaluated research investigation.
Source: Queensland Curriculum & Assessment Authority, Biology subject report, 2025 cohort (January 2026).
