A psychologist investigates whether an encouraging comment improves performance on a spatial puzzle. Different volunteers take part in each condition. Every volunteer has five minutes to complete the same 20-piece puzzle.
One group is told, ‘You are doing well; keep going.’ The other group is told, ‘Two minutes have passed.’
Before the task, each volunteer reports how many similar puzzles they completed during the previous month.
| Condition | Mean number of similar puzzles completed in the previous month | Mean number of pieces placed correctly out of 20 |
|---|---|---|
| Encouraging comment | 5.8 | 15.2 |
| Neutral comment | 1.6 | 10.1 |
The psychologist concludes that the encouraging comment caused volunteers to place more pieces correctly.
Using the data, explain one reason why the experimental design weakens the psychologist’s conclusion and one reason why it strengthens the psychologist’s conclusion.
182 exam-style questions on OCR GCSE Psychology 7.1 Planning Research, covering 7.1.1 Hypotheses, 7.1.2 Variables, 7.1.3 Experimental Designs, 7.1.4 Populations and Sampling, 7.1.5 Ethical issues, and 7.1.6 Dealing with ethical issues and BPS Code. Each one has a worked solution and a mark scheme showing where the marks go.