Why scientific inquiry matters more in 2026
The 2026 MOE Primary Science syllabus places significantly greater emphasis on inquiry skills compared to previous years. The PSLE examiners have explicitly increased the proportion of questions that test a student's ability to design experiments, identify variables, write hypotheses and interpret data — not just recall facts.
In past years, most students could rely on content knowledge alone to score well. In 2026, students who cannot answer inquiry questions accurately will lose marks that content knowledge cannot recover. A student who knows every fact about photosynthesis but cannot correctly identify the independent variable in an experiment will lose marks that previously they would have kept.
Inquiry questions appear in both Paper 1 (MCQ) and Paper 2 (open-ended). In Paper 2, inquiry questions typically carry 2–4 marks each and require precise language — not general descriptions. Vague answers like "it's a fair test" or "change the light" earn zero marks.
The three variables: IV, DV and CV
Every fair test experiment involves three types of variable. Students who confuse them lose marks consistently. Learn these definitions exactly — PSLE examiners look for specific vocabulary.
| Variable type | What it means | How to identify it | Example |
|---|---|---|---|
| Independent Variable (IV) | The one factor you deliberately change to test its effect | Ask: "What am I changing in this experiment?" | Amount of fertiliser added to plants |
| Dependent Variable (DV) | What you measure or observe — it depends on the IV | Ask: "What am I measuring to see the result?" | Height of the plant after 4 weeks (in cm) |
| Controlled Variable (CV) | All other factors kept the same throughout | Ask: "What else could affect the DV that I must keep constant?" | Type of plant, amount of water, temperature, pot size, soil type |
Students often confuse the independent variable with the dependent variable. A quick way to check: the IV causes the change; the DV shows the change. You control the IV; you measure the DV. If you changed it — it's the IV. If you measured it — it's the DV.
Be specific with the dependent variable
This is the single most common mark-losing error in inquiry questions. Examiners require a specific, measurable DV — not a vague description.
"Growth" is not measurable. "Height in centimetres after four weeks" is. Always state what you are measuring and how.
What makes a test fair
A fair test is an experiment in which only the independent variable is changed, and all other variables (controlled variables) are kept the same. This ensures that any change in the dependent variable can be attributed only to the independent variable — not to any other factor.
How to explain why a test is fair
When asked "how would you make this a fair test?" or "why is this experiment a fair test?", you must name specific controlled variables — not just say "everything else is kept the same."
When listing controlled variables, aim for at least three specific ones. Generic answers like "we keep everything the same" earn zero. Name the actual variables relevant to that experiment — think about what else could affect the dependent variable.
How to write a hypothesis
A hypothesis is a testable prediction that links the independent variable to the dependent variable and gives a reason. It is not just a guess — it must be falsifiable (capable of being proven wrong by evidence).
Worked examples of hypotheses
Experiment: Testing the effect of light intensity on the rate of photosynthesis in pondweed.
Experiment: Testing whether the surface area of a solid affects how fast it dissolves in water.
Do not start a hypothesis with "I think the plant will grow better" or "I think it will be faster." These are too vague. Name the IV explicitly, name the DV explicitly, state the direction of change (increase/decrease), and give a reason using a scientific concept.
Reading and interpreting data
PSLE 2026 places new emphasis on data interpretation — reading tables, graphs and results to identify patterns, explain trends and spot anomalies. These skills appear in both Paper 1 and Paper 2.
Describing a trend from a table or graph
When asked to describe what the data shows, always:
- State the direction of the relationship (as X increases, Y increases/decreases)
- Quantify where possible (from X = 10 to X = 50, Y doubled)
- Note any anomalous results (one reading that does not fit the pattern)
Identifying an anomalous result
An anomalous result is a reading that does not fit the pattern of the other results. When asked what to do with an anomalous result, you should: identify it as anomalous, exclude it from your calculation of the mean, and suggest it may be due to experimental error (not simply "a mistake").
Writing conclusions and evaluations
A conclusion must refer back to the hypothesis. It states whether the results support or do not support the hypothesis, and uses specific data from the results as evidence.
Always say "support" or "do not support" — not "prove." Scientific results support or do not support a hypothesis; they never prove it definitively. Examiners mark "proved" as imprecise and may deduct a mark.
Model answers — 6 full exam questions
Question 1 (1 mark): Identifying the independent variable
A student tests whether the colour of light affects the growth rate of algae. She grows algae under red, blue, green and white light for two weeks and measures the mass of algae at the end.
Q: What is the independent variable in this experiment?
Note: "light" alone is not enough — specify "the colour of light" to show you understand exactly what is being changed.
Question 2 (1 mark): Identifying the dependent variable
(Same experiment as above)
Q: What is the dependent variable? State how it is measured.
Question 3 (2 marks): Naming two controlled variables
Q: State two variables that must be kept the same in this experiment to make it a fair test.
2. The initial mass of algae at the start of the experiment must be the same for all groups. (1 mark)"
Also acceptable: temperature of the water, amount of nutrients, volume of water, duration of the experiment.
Question 4 (2 marks): Writing a hypothesis
Q: Write a hypothesis for this experiment.
Question 5 (2 marks): Describing results and identifying a trend
Results: Red = 12 g, Blue = 28 g, Green = 7 g, White = 18 g
Q: Describe what the results show.
Question 6 (2 marks): Writing a conclusion
Q: Do the results support the hypothesis? Explain using evidence from the results.
Key points to remember — Scientific Inquiry 2026
- IV = what you change. DV = what you measure. CV = what you keep the same.
- Always be specific: "height in centimetres" not "growth."
- A fair test means only the IV changes — name at least 3 specific CVs.
- A hypothesis must state IV, DV, direction of change and a scientific reason.
- Use "support" or "do not support" — never "prove."
- Describe trends using the data: state direction and include specific numbers.
- Anomalous results should be identified, excluded from the mean, and noted as possible experimental error.
- Conclusions must refer back to the hypothesis and cite specific evidence from the results.
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