Mr flannery's math class averaged poorly on a test, so he gave them a retest. there are 30 students in his class. on the retest, 10 students gained 15 points each, 10 students gained 5 points each, and 10 students lost 5 points each. how does the mean of the retest scores compare to the mean of the scores on the first test? a) the means are the same. b) the mean on the retest is 5 points higher. c) the mean on the retest is 10 points higher. d) the mean on the retest is 15 points higher.