Lesson focus: A fair investigation changes one factor while measuring a clear outcome.
Recognise enquiry types and distinguish a testable question from an unfocused one.
Build on earlier learning
Introduction and safetyRevisit the route from an observation and question to evidence and conclusion.
Planning an investigation?
Design an investigation with CORMMSSA step-by-step Logic Lab guide to planning a fair test, with a worked example and practice.
Practical
Designing a fair investigation
- Write a question with one independent variable and one dependent variable.
- List the control variables and how each is kept the same.
- Choose at least five values of the independent variable, spread across the range.
- Repeat each measurement three times and calculate a mean.
Record: A results table with units in the headings, then a line graph if both variables are continuous.
You will be successful when you can…
- Recognise five common types of scientific enquiry.
- Write a focused question answerable with evidence.
- Explain when a fair test is and is not appropriate.
- Choose an outcome that can be observed or measured.
Words that carry the science
- comparative test
- An enquiry comparing categories or conditions.
- fair test
- A test changing one independent variable while controlling relevant others.
- pattern seeking
- Looking for an association when variables cannot all be controlled.
- observation over time
- Recording how a system changes across a period.
- secondary research
- Using trustworthy evidence collected by other people.
Match the enquiry to the question
01Science uses more than fair tests
A fair testA test where you change only one thing and keep everything else the same, so you know what caused any difference. deliberately changes one factor and controls relevant others. It is useful for questions such as how temperature affects dissolving time.
comparative testAn investigation that compares different things or conditions, such as which paper towel soaks up the most water. compare groups, pattern seekingAn investigation that looks for links between things you cannot fully control, such as hand span and height. looks for associations, observation over timeAn investigation where you watch and record how something changes over days, weeks or longer, such as a seedling growing. follows change, identification and classification organise observations, and secondary researchUsing information that other people have collected, such as from trusted websites or books. draws on existing sources.
Be careful with pattern seekingAn investigation that looks for links between things you cannot fully control, such as hand span and height.. Two things can happen together without one causing the other. People wear sunglasses and sun cream on the same days, but sunglasses do not cause sun cream: sunny weather causes both.
02Make the question answerable
“Which towel is best?” is vague. “Which towel absorbs the greatest mass of water per square centimetre?” defines a measurable outcome and a fair comparison.
A good question fits the time, equipment and ethical limits available. Astronomers cannot move stars, so they observe and analyse patterns instead.
03Choose evidence before procedure
First decide what evidence would answer the question. Then choose measurements, observations, categories or sources that can provide it.
A clear outcome prevents “better”, “healthier” or “stronger” from hiding several different meanings.
The question determines the enquiry type.
- Fair/comparative testChange or compare conditions and measure an outcome.
- Pattern seekingMeasure naturally varying factors and look for association.
- Observe over timeRecord changes at planned intervals.
- Identify/classifyUse features to organise or name specimens.
- Secondary researchCompare relevant evidence from reliable sources.
Turn “best” into evidence
Improve the question “Which insulating material is best?”
- Define what “best” means: smallest temperature decrease.
- Name the comparison: equal layers of different materials.
- Fix a time period: 10 minutes.
- Write: “How does insulating material affect the temperature decrease of 100 mL of hot water over 10 minutes?”
How to make the reasoning visible: Operationalise vague words by replacing them with something observable or measurable.
Choose the enquiry
Match each question to the strongest main enquiry type.
| Question | Enquiry type |
|---|---|
| How does ramp height affect travel distance? | Fair test |
| Is foot length associated with height in this class? | Pattern seeking |
| How does a seedling change across 14 days? | Observation over time |
| Which leaf belongs to which local tree? | Identification/classification |
| How has atmospheric carbon dioxide changed since 1960? | Secondary research |
A class looks at whether people with longer feet are taller. Why is this not a fair test? (In a fair testA test where you change only one thing and keep everything else the same, so you know what caused any difference., you change one thing yourself.)
Rewrite “Which ramp is best?” as a fair-test question.
Use the table. Why is “How does a seedling change across 14 days?” an observation over timeAn investigation where you watch and record how something changes over days, weeks or longer, such as a seedling growing. and not a fair test?
Check your understanding
Answer from memory, then check against the suggested answer.
What is a fair test?
When do scientists use pattern seeking?
What makes a question testable?
What is a comparative test?
What is secondary research?
You want to find out how the shape of the Moon changes over one month. Which type of enquiry should you use? Give a reason.
People carrying umbrellas are often wearing coats too. Does carrying an umbrella make people wear coats? Explain.
Why can astronomers not do a fair test on stars? What can they do instead?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
You have some paper helicopters, scissors, a ruler and a stopwatch.
Suggest a question you could test. Start: “How does the … affect …?”
(1)What will you measure, and how?
(1)Give one thing you will do to make the comparison fair or trustworthy.
(1)Total for this question: 3 marks
Command word: For suggestA command word: use what you know to give a sensible idea, even about a situation you have not seen before., give a sensible idea that would work with the equipment you have.