GCSE-ready- Home
- Lessons
- GCSE Psychology
- Thinking like a scientist: variables, fair tests and hypotheses
Thinking like a scientist: variables, fair tests and hypotheses
🎬 The doodle video for this lesson is coming soon. Subscribe on YouTube to see it first.
In KS3 science you planned fair tests. Psychology experiments work the same way, with people instead of test tubes.
Variables
Independent variable (IV): the thing the researcher changes (like the temperature in a science test).
Dependent variable (DV): the thing that is measured (like how fast a reaction happens).
Control variables: everything else, kept the same so the test is fair.
In psychology, things that could spoil the test are called extraneous variables, for example noise, time of day or how tired participants are.
Dependent variable (DV): the thing that is measured (like how fast a reaction happens).
Control variables: everything else, kept the same so the test is fair.
In psychology, things that could spoil the test are called extraneous variables, for example noise, time of day or how tired participants are.
Fair tests with people
People differ in many ways, so psychologists use extra controls:
Standardised instructions: everyone hears exactly the same words.
Random allocation: chance decides who goes in which group, so groups are similar.
Repeating with many participants and taking an average makes results more trustworthy, just as repeating readings did in KS3 science.
Standardised instructions: everyone hears exactly the same words.
Random allocation: chance decides who goes in which group, so groups are similar.
Repeating with many participants and taking an average makes results more trustworthy, just as repeating readings did in KS3 science.
Hypotheses
A hypothesis is a precise, testable prediction. It names both variables.
Example: 'Pupils who revise with music playing will recall fewer words out of 20 than pupils who revise in silence.'
Compare a vague prediction: 'music affects memory'. You cannot test that properly, because it does not say what is measured.
Example: 'Pupils who revise with music playing will recall fewer words out of 20 than pupils who revise in silence.'
Compare a vague prediction: 'music affects memory'. You cannot test that properly, because it does not say what is measured.
A researcher tests whether caffeine affects reaction time. Name the IV and DV.
- The researcher changes whether people have caffeine.
- The researcher measures reaction time.
Answer: IV: whether participants have caffeine or not. DV: reaction time.
The IV is changed, the DV is measured and other variables are controlled to make a fair test. Psychologists add standardised instructions and random allocation. A hypothesis is a precise, testable prediction naming the IV and DV.
The interactive lesson includes the diagrams for this topic.
Check you have got it
Answer 6 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.