Power calculation
Based on a study that examined the physiological impact of wearing an
N95 mask during hemodialysis8, with a sample size of
41 pairs (of observations), we have 85% power and a level of
significance of 5% (two-sided) for detecting a mean of differences of
9.0 mmHg in PaO2 between pairs, assuming a standard
deviation of the differences to be 18.5.