I am designing a pain study. The outcome is change in pain from a Numeric Rating Scale (NRS), 0-11, pre- and post- treatment. Our original thought was to hypothesize a change of at least 2.0, with a standard deviation of 4.0 yielding an effect size of 0.5, requiring 34 subjects. However, we thought about changing this to a change in NRS of 30%, so 1-3 would be at least one point, 4-6 at least 2 points, 7-10 at least 3 points. This makes the outcome binary. There is no control group. I was unsure of how to translate this into an odds ratio for the hypothesis and power calculation. If there's a direct translation or an approximate "medium" odds ratio that could be justified in the same way an effect size of 0.5 is "medium", and how to set up the other parameters: P(Y=1|X=1) Also what the R^2 Other X is, and the X parm pi (proportion). I'm using G*Power 188.8.131.52 and logistic regression, trying to get the entire confidence interval over 1.