I need some help understanding what values I need to put into a two-tailed logistic regression power analysis are in G*Power. I am trying to see if hypertension (my binary independent) makes a difference on having a headache (my binary dependent).
The prevalence of having a headache, irrespective of hypertension is 0.004 (from [0-1]). I assume this is my null hypothesis P(headache=1|hypertension=1) i.e., hypertension does not impact the outcome of a headache.
The prevalence of a patient having a headache with hypertension if 0.332. I assume this is my alternative hypothesis P(headache=1|hypertension=1).
Is this what I need to add into the probability textboxes, and what do I add into the X param pi (I think this is the proportion of some distribution)?
Further edit: I have a medical population. I am only interested in records with a headache diagnosis, but I want to determine what set size I require measuring an increase or decrease in odds given the presence (exposure) to hypertension. I already know from the literature that your odds go up! And my piolet study shows that hypertension is the most prevalent of comorbidities in the headache cohort.