Cognition and BehaviourResearch MethodsExperimental DesignIndependent GroupsRepeated Measures
AQA GCSE · Question 24 · Cognition and Behaviour
Outline what is meant by independent groups and repeated measures.
Discuss the strengths and weaknesses of both of these types of experimental design.
How to approach this question
This question has two parts: outlining the designs and discussing their pros and cons.
1. **Outline (approx. 2-3 marks):**
* Provide a clear and concise definition for 'independent groups design'. Mention that different participants are in each condition.
* Provide a clear and concise definition for 'repeated measures design'. Mention that the same participants are in all conditions.
2. **Discussion (approx. 6-7 marks):**
* Create a section for Independent Groups. State one clear strength (e.g., no order effects) and explain it. State one clear weakness (e.g., participant variables) and explain it.
* Create a section for Repeated Measures. State one clear strength (e.g., controls for participant variables) and explain it. State one clear weakness (e.g., order effects) and explain it. Mention a way to control for the weakness (counterbalancing).
Full Answer
Experimental design refers to how participants are allocated to the different conditions in an experiment.
- **Independent Groups:** Uses two or more separate groups of participants. For example, Group A gets a new drug, Group B gets a placebo. Strength: No order effects. Weakness: Individual differences between groups (participant variables) can confound the results.
- **Repeated Measures:** The same group of participants is tested under all conditions. For example, a group's memory is tested, they are taught a new technique, and then their memory is tested again. Strength: Controls for participant variables. Weakness: Order effects (like practice or fatigue) can confound the results. This is often managed using counterbalancing.
- A third type is **Matched Pairs**, which tries to get the best of both worlds by matching participants on key variables before randomly allocating one of each pair to a different condition.
Common mistakes
Muddling the definitions of the two designs. Confusing the strengths and weaknesses of each. Forgetting to discuss both designs.
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