The manager of a call center randomly selected 20 employees to attend training sessions that teach employees how to assist customers quickly. The manager also selected 20 other employees as a...

The manager of a call center randomly selected 20 employees to attend training sessions that teach employees how to assist customers quickly. The manager also selected 20 other employees as a comparison group. After the training was completed, the manager used regression to compare the two groups. The response is the average length of time (in minutes) required by the 40 employees to resolve calls during the next week. The single explanatory variable Attend is coded 1 for those who attended the training sessions and 0 for those who did not. This table summarizes the least squares regression.

a. How long on average do those who did not attend the training spend on a call? What is the average length for those who did attend the training?
¹

b. If one were to compare the average length of calls for those who attended the sessions to that for those who did not using a pooled two-sample
-test, what would be the
-value of that test? Would that test find a statistically significant difference between the means?
²

c. What is missing from this comparison of the two groups?
³