Minimum detectable effect size for main outcomes (accounting for sample
design and clustering)
around 4,000 for each arm
Minimum detectable size: Assuming 40,000 observations, wee expect a 40% read rate and a 5% visit rate. Based on this we will be able detect 1.59% and 0.73% differences in the base rates (using the Stata Codes below).
. power twoproportions 0.40, alpha(0.05) power(0.9) n(40000)
Performing iteration ...
Estimated experimental-group proportion for a two-sample proportions test
Pearson's chi-squared test
Ho: p2 = p1 versus Ha: p2 != p1; p2 > p1
Study parameters:
alpha = 0.0500
power = 0.9000
N = 40000
N per group = 20000
p1 = 0.4000
Estimated effect size and experimental-group proportion:
delta = 0.0159 (difference)
p2 = 0.4159
. power twoproportions 0.05, alpha(0.05) power(0.9) n(40000)
Performing iteration ...
Estimated experimental-group proportion for a two-sample proportions test
Pearson's chi-squared test
Ho: p2 = p1 versus Ha: p2 != p1; p2 > p1
Study parameters:
alpha = 0.0500
power = 0.9000
N = 40000
N per group = 20000
p1 = 0.0500
Estimated effect size and experimental-group proportion:
delta = 0.0073 (difference)
p2 = 0.0573