Problem
The American Orthopedic and Ankle Society is going to conduct a survey of randomly selected working women. One of the questions is: Do you usually wear flats to work? If they wish to estimate the proportion of women who wear flats to work within a margin of error of .02 with 95% confidence, how large must their sample be?
What do I know? What do I want to find? What do I expect the answer to be? How do I go from what I know to what I want to find out? Does this answer seem reasonable?