A sports scientist investigated the effect of different hydration drinks on reaction and coordination speeds during physical exercise. She obtained a volunteer sample of 36 amateur league squash players by posting a recruitment message on a regional squash club's private online forum.
All participants completed a high-intensity coordination drill under two different hydration conditions on separate days:
Condition X: The participant consumed 500 ml of an isotonic sports drink 30 minutes before the drill (isotonic condition).
Condition Y: The participant consumed 500 ml of plain tap water 30 minutes before the drill (water condition).
The median completion time (in seconds) and the median number of coordination errors recorded for each condition are shown in Table 1.
Table 1 Median drill completion times and coordination errors
| Condition X: Isotonic | Condition Y: Water | |
|---|---|---|
| Median completion time (seconds) | 42.5 | 48.2 |
| Median number of coordination errors | 2 | 5 |
Explain one strength and one limitation of using volunteer sampling in this study.
689 exam-style questions on AQA A Level Psychology Scientific processes. Each one has a worked solution and a mark scheme showing where the marks go.