Research Design, Sampling and Ethics
Before you trust a psychology finding, you check how it was made. Learn to spot the variables, choose a design and a sample, and follow the rules that protect the people who take part.
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How to trust a study 🔬
A psychology finding is only as good as the way it was produced. Before you believe "X causes Y", you ask three questions: was the research **well designed**? Was the **sample fair**? Was it done **ethically**? This module walks through all three - variables and hypotheses, experimental designs and sampling methods, and the rules that protect the people who take part.
Variables 🎛️
Every experiment turns on these. The first two are what the study is about; the rest are what can spoil it if left uncontrolled.
Find the variable 🎯
Researchers test whether drinking caffeine changes people's reaction time. What is the independent variable?
- Whether or not the participants have caffeine
- The reaction time that is measured
- The temperature of the room
- The age of the participants
Match each variable to an example 🔗
- Independent variable
- Dependent variable
- Situational variable
- Participant variable
- The amount of caffeine the researcher gives
- The reaction time that is measured
- Background noise in the testing room
- A participant's age or mood
Null or alternative? 🧪
A hypothesis states: "There will be no difference in reaction time between the caffeine and no-caffeine groups; any difference is due to chance." What kind of hypothesis is this?
- A null hypothesis, because it predicts no difference
- An alternative hypothesis, because it predicts a difference
- A directional hypothesis, because it states a direction
- An extraneous variable
Two ways to use your participants 👥
In an experiment you compare conditions, and the design decides WHO does each one. A third design, **matched pairs**, uses different but closely matched participants to combine the strengths of both.
Beating order effects ✅
In a repeated measures design, participants might improve with practice or tire with fatigue. Select the TWO techniques that control these order effects.
- Counterbalancing - half do condition A first, half do B first
- Randomising the order in which participants do the conditions
- Standardising the instructions given to everyone
- Using a single-blind procedure
Choosing a sample 👣
You cannot test everyone in the target population, so you take a sample. How you pick it decides how representative your results are.
Match each sampling method 🧩
- Random sampling
- Stratified sampling
- Volunteer sampling
- Opportunity sampling
- Every person has an equal chance, for example names drawn from a hat
- Subgroups appear in the same proportions as in the population
- People reply to an advert and put themselves forward
- Whoever happens to be available is asked
The rules that protect people 🛡️
Research uses real people, so it follows ethical guidelines. Learn these five: **Informed consent** - participants agree knowing what is involved. **Deception** - do not mislead them; if some is unavoidable, explain fully afterwards. **Confidentiality** - keep their data private and anonymous. **Right to withdraw** - they can leave at any time and remove their data. **Protection of participants** - they should come to no physical or psychological harm.
Run it properly 🪜
An interactive activity.
The ethical call 🧭
An interactive activity.
The summary 📝
The variable a researcher changes is the _____, and the one they measure is the _____. A _____ hypothesis predicts no difference. In a repeated measures design, order effects are controlled by _____. And the sampling method where people reply to an advert is called _____ sampling.
Your turn ✍️
An interactive activity.