8.30 Suppose that, in a survey of 600 employers, 126 indicate that
they have used a recruitment service within the past two
months to find new staff.
a. Construct a 95% confidence interval for the population
proportion of employers who have used a recruitment
service within the past two months to find new staff.
b. Construct a 99% confidence interval for the population
proportion of employers who have used a recruitment
service within the past two months to find new staff.
c. Interpret the intervals in (a) and (b).
d. Discuss the effect on the confidence interval estimate when
you change the level of confidence.
