Question 8.44

8.44 Are the customers dissatisfied?

A cell phone manufacturer would like to know what proportion of its customers are dissatisfied with the service received from their local distributor. The customer relations department will survey a random sample of customers and compute a 95% confidence interval for the proportion that are dissatisfied. From past studies, the department believes that this proportion will be about 0.09.

  1. Find the sample size needed if the margin of error of the confidence interval is to be about 0.02.
  2. Suppose 12% of the sample say that they are dissatisfied. What is the margin of error of the 99% confidence interval?