Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes.Assume that the population standard deviation is 4 minutes.The 95% confidence interval for the population mean of waiting times is ________.
A)14.02 to 15.98
B)7.16 to 22.84
C)14.06 to 15.94
D)8.42 to 21.58
E)19.80 to 23.65

Question

Quizplus · Accepted Answer

The correct answer is A.The 95% confidence interval for the population mean of waiting times is 14.02 to 15.98. This is calculated using the formula:CI = x̄ ± z * (σ / √n)where x̄ is the sample mean, z is the z-score for the desired confidence level, σ is the population standard deviation, and n is the sample size.In this case, x̄ = 15, z = 1.96 (for a 95% confidence level), σ = 4, and n = 64. Plugging these values into the formula, we get:CI = 15 ± 1.96 * (4 / √64)CI = 15 ± 1.96 * (4 / 8)CI = 15 ± 1.96 * 0.5CI = 15 ± 0.98CI = 14.02 to 15.98

Brian Vanecek, VP of Operations at Portland Trust Bank, Is