Example Answer for Question 21 Paper 2: AS Psychology, June 2017 (AQA)

Section C - Research Methods

Question 21: Identify & Explain [3 Marks] - Extraneous Variables

Suggested Answer: One possible extraneous variable that the psychologists should have controlled is the time of day when completing Task A (Silence) and Task B (Music).

If the psychologist did not control this variable, then the participants who completed the experiment earlier in the day may find the 10 differences in the spot the difference puzzle faster because they are more alert. Consequently, this might make the results less valid because the experimenter might not be measuring the effect of Silence or Music, and might in fact be measuring alertness. 

Please Note: These answers have been produced without the knowledge of the mark scheme and merely reflect my attempt at producing a model answer on the day of the exam. These answers are not endorsed or approved by AQA.