Question

A credit card company operates two customer service centers. Callers to the service centers dial a single number, and a computer program routes callers to the center having the fewest calls waiting. As part of a customer service review program, the credit card center would like to determine whether the average length of a call (not including hold time) is different for the two centers. The managers of the customer service centers are willing to assume that the populations of interest are normally distributed with equal variances. Suppose a random sample of phone calls to the two centers is selected and the results that were reported are shown below. Complete parts a and b. Center A Center B Sample Size Sample Mean (seconds) Sample St. Dev. (seconds) 100 150 57.4 65.2 7.7 6.8 a. Using the sample results, develop a 95% confidence interval estimate for the difference between the two population means. Let sample 1 be the sample from Center A and let sample 2 be the sample from Center B. (2 (Round to two decimal places as needed.)

Answer 1

The statistic software output for this problem is:

Two sample Z summary confidence interval: Hi : Mean of population 1 (Std. dev. = 7.7) 2: Mean of population 2 (Std. dev. = 6.8) Pi-N2 Difference between two means 95% confidence interval results: Difference ni n2 Sample mean Std. err. L. limit U. limit H1 - H2 100 150 -7.8 0.94929799 -9.6605899 -5.9394101

-9.66
<μι – μ2 <
-5.94