Aim 1 - within group analysis sample size
A sample size of 21 achieves 90% power to detect a mean of paired differences of 3.0 with a significance level of 0.05 using a two-sided paired t-test. A sample size of 34 achieves >90% power to detect a difference of 3.0 with a significance level of 0.05 using a two-sided Wilcoxon Signed-Rank test. Assuming at least 20% of the sample changes between baseline and follow-up a sample size of 115 pairs achieves 80% power to detect an odds ratio of 3.0 using a two-sided McNemar’s test with a significance level of 0.05. The odds ratio is equivalent to a difference between two paired proportions of 0.10.