A researcher investigates the effect of caffeine on motor coordination by measuring the time (in seconds) taken by 30 participants to complete a precision manual task. Before choosing a statistical test, the researcher notes that the standard deviation is 1.2 seconds for the caffeine group and 4.8 seconds for the placebo group, and the scores in both groups show a strong positive skew.
Which of the following explains why a parametric test is not suitable for analyzing these data?
The data are measured on a ratio scale (seconds), whereas parametric tests require nominal or ordinal data.
The standard deviations are too similar, and the sample size is too small for a parametric test.
The data violate the assumptions of a normal distribution and homogeneity of variance.
Parametric tests can only be used if the research uses a repeated measures design, whereas this study uses an independent groups design.
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.