A sports scientist wanted to investigate whether consuming beetroot juice improves aerobic performance during a middle-distance run.
The scientist recruited 15 experienced club runners for a study using a repeated measures design. In Condition A, participants drank 200 ml of concentrated beetroot juice 2 hours before a 400m time trial. In Condition B, participants drank 200 ml of a taste-matched placebo juice (which did not contain the active nitrates of beetroot) 2 hours before a 400m time trial.
To allow for a wash-out period, the two trials were conducted exactly one week apart at 09:00 AM on an outdoor running track. The scientist recorded the time taken (in seconds) to complete each 400m run.
Identify one extraneous variable that could have affected the results of this study. Suggest why it would have been important to control this extraneous variable and how it could have been controlled 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.