A computer manufacturer has toll-free numbers that customers may use to call for help with problems related to their computer. The service manager expects that the proportion of calls that will be answered within 5 minutes exceeds 80%. He conducted a survey recently. In a random sample of 70 calls, he found that 54 calls were answered within 5 minutes.

Part 1:

1. Compute a 90% confidence interval for the population proportion of all customer calls, which are answered within 5 minutes.
2. According to the 90% confidence interval you found in (a), could we conclude that the service target has been reached? Explain.
3. For part (a), what sample size should be used if we want a 90% confidence interval within +/- 5%?

Part 2:

1. Using a significance level of 5%, conduct a test to determine if the service target has been met. Use a critical value approach.
2. Determine the p-value for the test statistic in part a.