A sports scientist conducted a study to investigate whether consuming a high-caffeine energy gel 15 minutes before a run improves the 5km running times of recreational athletes. An independent measures design was used, testing a small sample of 12 runners. Half of the participants consumed a gel containing 150 mg of caffeine, while the other half consumed an identical-looking placebo gel containing no active ingredients. The data obtained from the study is presented in the table below.
| 5km Running Times (in minutes) with Caffeine Gel or Placebo Gel | |||
|---|---|---|---|
| Caffeine Gel | Placebo Gel | ||
| Participant | Time (mins) | Participant | Time (mins) |
| 1 | 21.5 | 1 | 24.2 |
| 2 | 19.8 | 2 | 26.1 |
| 3 | 22.0 | 3 | 23.5 |
| 4 | 18.5 | 4 | 25.0 |
| 5 | 20.2 | 5 | 22.8 |
| 6 | 19.4 | 6 | 24.7 |
Outline what is meant by the following feature of science and state how it applies to this study.
Manipulation of variables
