A retail company is interested in examining whether the time taken for it to obtain approval for a credit card number by phone varies from one day of the week to another. The manager collects the following results. On Mondays, a sample of n1 = 20 cases had a sample average of 1 = 20.44 seconds with a sample standard deviation of s1 = 1.338 seconds. On Wednesdays, a sample of n2 = 15 cases had a sample average of 2 = 16.33 seconds with a sample standard deviation of s2 = 1.267 seconds, and on Fridays, a sample of n3 = 18 cases had a sample average of 3 = 15.34 seconds with a sample standard deviation of s3 = 1.209 seconds. What should the manager conclude?