how to calculate sample size with 95 confidence interval?
['za/2: Divide the confidence interval by two, and look that area up in the z-table: .95 / 2 = 0.475. ... ', 'E (margin of error): Divide the given width by 2. 6% / 2. ... ', ': use the given percentage. 41% = 0.41. ... ', ': subtract. from 1.']