Hi all,
I received an email from a few students for clarification on Question 3. The question really is about thinking about the assumptions you'd need to estimate in order to calculate your sample size. One of the main assumptions for sample size calculations is to provide an educated estimate the expected outcome in the control group (based on prior studies or literature). For most published trials, investigators will provide their a priori assumptions of the outcome in the manuscript or in the appendix. As such for question 3, please provide the following:
3ai. According to investigators, what were their assumptions of the outcome in the control group that led to the sample size calculations? Please include the type of outcome (incidence, prevalence, mean), the follow-up period that would be used to calculate outcome (if at one time-point, indicate it as so), and if relevant, the expected distributional variability (e.g. standard deviation). For example, the Aspire trial assumed an annual HIV-incidence infection rate of 3.9% in the placebo group and that all participants were followed for >= 12 months. (Please note that their assumptions may not equal what they actually found in the trial).
3aii. In the trial itself, what was their proposed analysis to estimate the primary outcome? For example, the Aspire Trial estimated the within-arm annual incidence of HIV-1 infection using the Kaplan-Meier method.
Let me know if you have any further questions.
Michelle