You want to estimate the proportion of adults who make over $50,000 a year in your county. According to a study done two years ago, the proportion is .18, and you suspect the proportion hasn't changed. 
 You need a margin of error of no more than ± 2%. 
 Which of these expressions would give you your minimum sample size? 
 A. n = AP Statistics Semester 2 Non-AP Pre-Calculus Semester 1 .18(1 - .18) 
 B. n = AP Statistics Semester 2 p(1 - p) 
 C. n = AP Statistics Semester 2 
 D. n = AP Statistics Semester 2 
 E. Can't be determined