Lesson focus: A strong scientific question is precise enough to investigate and meaningful enough to matter.
Convert an observation into a question that can be answered with evidenceObservations or measurements used to show whether an idea is right or wrong..
Build on earlier learning
Scientific investigationsRevisit how the enquiry type must match the scientific question.
You will be successful when you can…
- Distinguish scientific questions from preference questions.
- Replace vague outcomes with measurable definitions.
- Check that a question is feasible and ethical.
- Explain how measurement choice affects validity.
Words that carry the science
- testable question
- A question answerable using obtainable observations or measurements.
- operational definition
- A precise statement of how an idea will be measured.
- validity
- How well evidence and method address the intended question.
- feasible
- Possible with the available time, equipment and conditions.
- ethical
- Consistent with responsible treatment of people, organisms and environments.
Write questions that evidence can answer
01Move from preference to measurement
“Which towel is best?” may mean strongest, cheapest or most absorbent. A testable questionA question you can answer by doing an investigation and collecting measurements. replaces “best” with a defined outcome, such as the mass of water absorbed per square centimetre.
This measurement rule is an operational definitionA clear statement of exactly how you will measure something, such as "time until the cross can no longer be seen".. It lets different investigators collect comparable evidence.
02Ask what the evidence can support
A question should name the comparison or factor and a measurable outcome. It must also be feasiblePossible to do with the time, equipment and space you have. with the available range, resolution and time.
ethicalFair and responsible towards people, animals and the environment. limits matter. Do not cause avoidable harm or collect personal information simply because it could be measured. Use safe models, non-invasive observations or reliable secondary evidence when appropriate.
When you can only measure two things, not change one of them, say they are associated withLinked to: the two things tend to happen together, but one does not have to cause the other. each other (they go together). Do not say one causeWhen one change actually makes another change happen, not just happens at the same time. the other.
03Protect validity
validityWhether an investigation really tests what it is meant to test. asks whether the evidence addresses the intended question. Timing how long a towel drips does not necessarily measure how much water it absorbed. In the same way, plant height alone misses growth of leaves and roots.
Before planning the method, explain why the chosen outcome represents the concept in the question.
Pass the idea through each check before writing the method.
- SpecificIs the comparison or factor clearly named?
- MeasurableIs the outcome defined by an observation or unit?
- ValidDoes that outcome represent the intended idea?
- FeasibleCan the evidence be obtained with available resources?
- EthicalCan it be done responsibly and safely?
Operationalise “strongest”
Improve “Which paper is strongest?”
- Decide what strength means in this context.
- Define an outcome: maximum mass supported before tearing.
- Standardise strip width and support spacing.
- Write: “How does paper type affect the maximum mass a 2 cm-wide strip supports before tearing?”
How to make the reasoning visible: A defensible question states exactly what counts as the outcome.
Question clinic
Diagnose each question and improve it.
| Original question | Problem | Improved version |
|---|---|---|
| Which drink is nicest? | Preference, not a scientific property | How does sugar concentration differ among named drinks? |
| Do big feet mean tall people? | Vague and causal wording | Is foot length associated with height in this sample? |
| Which towel absorbs most? | Area and measurement not defined | Which towel absorbs the greatest water mass per 100 cm²? |
| Does music make plants happy? | “Happy” is not operationally defined | How does sound treatment affect stem-height increase over 14 days? |
Why does the improved height question say “associated with” instead of “causes”? (associated withLinked to: the two things tend to happen together, but one does not have to cause the other. means the two things go together.)
Plant height is used to measure how much a plant grows. Give one problem with only measuring height.
Improve the question “Which paper towel is best?” so that it can be tested.
Check your understanding
Answer from memory, then check against the suggested answer.
What is an operational definition?
What is validity about?
What makes a question feasible?
What makes a question scientific?
Why is “Which drink is nicest?” not a scientific question?
Rewrite “Which shoe has the best grip?” so it can be measured.
Two groups measure “fitness”. Group A measures resting heart rate. Group B times a 1 km run. Why might they disagree about who is fittest?
Why is “Do big feet mean tall people?” improved to “Is foot length associated with height in this sample?”
Exam Question Practice
Exam Question Practice
Mark points shown after marking
You have identical cups, some insulating materials, a thermometer and a stopwatch. (Insulating materials slow down heat loss.)
Suggest a testable question you could answer with this equipment. Start: “How does the type of … affect …?”
(1)What is the dependent variable (the thing you measure)?
(1)Name one thing you should keep the same.
(1)Total for this question: 3 marks
Command word: A suggestA command word: use what you know to give a sensible idea, even about a situation you have not seen before. answer must work with the equipment you are given.