Testing about population mean.
The Rocky Mountain district sales manager of JCM, Inc., a college book publishing company, claims that each of his sales representatives makes 40 calls on professors per week. Some reps said that this estimate is too low. To research claim, a random sample of 28 reps revealed that the mean number of calls made last week was 42. The standard deviation of the sample was computed to be 2.1 calls. At the .05 level of significance, can we bring to a close that more than 40 calls are made on the average in a week?