In a 1983 Harris poll of n = 1250 individuals, the proportion who used seat belts was 0.19. In a 1992 poll of n

7) In a 1983 Harris poll of n = 1250 individuals, the proportion who used seat belts was 0.19. In a 1992 poll of n = 1251 individuals, the proportion who used seat belts was 0.70.

i) Find a 90% confidence interval for p1-p2 where p1 corresponds to the 1983 poll.

ii) Do you think that the (population) proportion was higher in 1992? Why?

Comment: Use the formula given in class (or ex. 8.8):

(p1 - p2) +- z_a/2...

Please see attached question