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How to Answer Experiment Questions

PSLE Science Experiment Questions: 5 Common Parts

Part 3 of 3 of the PSLE Science OEQ Guide: build a full experiment answer, using everything from Parts 1 and 2.

MCQ.SG Team··3 min read
PSLE Science Experiment Questions: 5 Common Parts

Fruit ripening. Yoghurt. Mosquito spray. An experiment question can use a very different story or set-up, but the same investigation skills return.

These are Booklet B questions built around an experiment. A question may show a set-up with variables, ask whether a comparison is fair, or give a table or graph of results. From 2026, Booklet B is worth 40 marks over 10 to 11 structured questions.

What the question is really asking

Three useful questions help you read an experiment: what am I testing?, is the comparison fair?, and what do the results show? Each part may ask you to use a different one.

The five parts

On the paper, look out for five common parts:

  1. The variables — name what was changed, what was measured, what was kept the same. What am I testing? → Episode 2
  2. The aim — both variables in one sentence. What am I testing? → Episode 3
  3. Fairness — change the variable being tested and keep other relevant conditions the same. A control set-up provides a comparison. Is the comparison fair? → Episode 4
  4. The data — describe the trend and use readings when asked for evidence. What do the results show? → Episode 5
  5. The fix — match the fix to the flaw, and keep the conclusion inside the data. The last two questions together. → Episode 6 and Episode 7

A question won't always ask all five. But learn to spot which one you're being asked for, and a strange new theme is just a new story around a set-up you've already practised.

Reading in order works too. Start with the variables in Episode 2. The later lessons use those variable names again.

Practice exampleA student wants to find out if the amount of sunlight a plant receives affects how fast it grows. She places three identical seedlings, in identical pots with identical soil and water, under lamps of different brightness (low, medium, high) for two weeks, then measures the height of each plant. Identify the five parts you need to answer this experiment question in full.
The answer we see all the time“The plant needs sunlight to grow well, so the one under the brightest lamp will grow the tallest.”
This goes straight to guessing an answer without first sorting out the question. It never names the changed variable, the measured variable, or which of the five parts (variables, aim, fairness, data, fix-and-conclusion) is being asked for. So if the real sub-questions come in an order you don't expect, there is nothing to help you.
One possible answer“This is a fair-test / experiment question. To answer it fully I would need to: (1) identify the changed variable (amount of sunlight) and measured variable (height of plant), and the controlled variables (type of plant, pot, soil, amount of water); (2) state the aim — to find out how the amount of sunlight affects the height of the plant; (3) check whether it is a fair test and whether a control set-up is needed; (4) read the height data across low/medium/high sunlight and state the relationship; (5) check if the experiment was repeated, and state a conclusion based on the data.” Naming all five parts first is the habit that scores in PSLE — it stops half of a multi-part question going unanswered.

What a strong answer does

  • Use one name for a variable all the way through. The parts are a set. Call it "the amount of fertiliser" in part (a), and call it that in part (b) and part (c) too. Keep the same name, and every part matches the one before it.
  • Sort the variables first, whatever the question asks first. Every other part uses them. The aim names two of them, and the fairness answer is about the ones kept the same. Thirty seconds spent naming them makes every later part quicker.
  • Read the instruction and check the marks. Marks help you judge the detail needed. They are not a sentence or fact count. Cover what the part asks for, with the relevant reasoning or evidence. See the seven answering mistakes.

If you want to try this on real questions, MCQ.SG marks open-ended questions point by point and gives feedback on every answer.

For more tips on improving your answers—from avoiding common mistakes to using precise science language—explore the complete PSLE Science OEQ Guide.

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PSLE Science Experiment Skills from P3 to P6

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PSLE Science: 3 Types of Experiment Variables

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