Sample Size Key (Even)

(2) n = (1.962)(.1)(.9) / (.0252) = 553

(4) Number of cases = Number of controls = 533

(6) Estimates differ slightly according to source formula. According to Dallal's table, use 219 in each group. Using EpiCalc 2000, use 198 in each group. Either way, "about 200" in each group of 400 total.