Table 1:

Primary components required for a sample size calculation

	What is it?	Specification
Type I error rate ($\alpha$)	The probability of falsely rejecting H0 (false-positive rate)	Conventional choices are $\alpha =$0.05 and 0.01
Power ($1\text{-}\beta$)	The probability of correctly rejecting H0 (true-positive rate), equivalent to 1 $\text{-}$ the Type II error rate ($\beta$)	Conventional choices are $\beta =$0.20 and 0.10
Minimal clinically relevant difference	The smallest (biologically plausible) difference in the outcome that is clinically relevant	Input from the researcher(s) responsible for the study for the effect of scientific interest
Variance	Variability in the outcome (e.g. standard deviation for continuous outcomes)	Use existing clinical knowledge (e.g. other published articles) or a pilot study