Describe the factors that determine the sample size of a randomised clinical trial  (60% of marks). Describe the differences between a parametric and a non-parametric statistical test and give one example of a parametric test and one example of a non-parametric test

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College Answer

The factors included the power of the study, variability of outcomes, acceptable p value, the
incidence of the outcome and the study design. An explanation of how each of these factors affected sample size was required e.g. if the incidence of the outcome is rare, a larger sample size is required.

Candidates failed because of lack of knowledge.

Syllabus EBM 2c
Reference: Gin and Myles p 24-29.