Spam e-mail has become a serious and costly nuisance. An office manager believes that the average amount of time spent by office workers reading and deleting spam exceeds 25 minutes per day. To test this belief, she takes a random sample of 18 workers and measures the amount of time each spends reading and deleting spam. The results are listed here (see attachment).

a)Describe the data visually and verbally, including confidence intervals for an appropriate measure of central tendency.

b)Can the manager infer at the 4% significance level that she is correct? Use both, a parametric and a non-parametric test. Validate the assumptions for each test. If the test results differ, which test would you rather rely on? What is the standardized effect size for this test? Discuss the result of the test and the magnitude of the effect size.