A sports science researcher wants to investigate the effect of background music on athletic endurance. Participants are asked to run on a treadmill to exhaustion while listening to either 'high-motivation' or 'low-motivation' music.
The researcher selected the music tracks himself, classifying them as 'high-motivation' or 'low-motivation' entirely based on his own personal opinion.
Explain how this study's methodology could be improved to increase the validity of this independent variable.
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.