A cognitive psychologist investigates whether cognitive performance varies with caffeine consumption. She measures the attention scores of 20 participants (on an interval scale that meets all parametric assumptions) first after drinking decaffeinated coffee, and then again after drinking caffeinated coffee.
Which inferential test should the psychologist use to analyze whether there is a significant difference between the two conditions?
Wilcoxon Signed Ranks test
Unrelated t-test
Related t-test
Mann–Whitney U test
644 exam-style questions on OCR A Level Psychology Research methods and techniques. Each one has a worked solution and a mark scheme showing where the marks go.