A psychologist is studying job satisfaction among all 240 bus drivers employed by one transport company. The drivers are based at three depots.
| Depot | Number of drivers |
|---|---|
| North | 120 |
| Central | 72 |
| South | 48 |
The psychologist writes each driver's name on an identical slip of paper. She keeps the slips from each depot in a separate container and draws 8 slips from each container.
Explain, using the data in the table, why this procedure does not give a random sample of the target population.
The psychologist tries to correct the procedure. She empties the slips still left in the three containers into one box, mixes them thoroughly and draws 24 slips without looking, setting each slip aside after it is drawn. She does not return the 24 slips drawn in the original procedure.
Explain, using a calculation, whether this change gives a random sample of the target population.
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.