Astatistics instructor who teaches a lecture section of 160 students wants to determine whether students have more difficulty with one-tailed hypothesis tests or with two-tailed hypothesis tests. on the next exam, 80 of the students, chosen at random, get a version of the exam with a 10-point question that requires a one-tailed test. the other 80 students get a question that is identical except that it requires a two-tailed test. the one-tailed students average 7.81 points, and their standard deviation is 1.06 points. the two-tailed students average 7.64 points, and their standard deviation is 1.33 points.