A student is investigating the subjective efficacy of two herbal sleep remedies. They recruit a sample of 22 participants suffering from mild insomnia. Each participant experiences two different trial conditions in a counterbalanced order over two weeks:
At the end of each 5-night period, participants rate their overall sleep quality on a subjective scale from 1 to 8 (1 = extremely poor sleep, 8 = excellent sleep).
The student wants to test for a significant difference in the sleep quality ratings between Condition A and Condition B. They propose using a Mann-Whitney U test to analyse the data.
Suggest a more appropriate statistical test of difference for the student to use with this data. Explain two reasons for your choice based on the description of the study.
121 exam-style questions on AQA A Level Psychology Inferential testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.