1. At a certain high school, a random sample of 50 student are chosen for a free 10-week SAT prep class They are given a pre-test before the course begins and a post-test after taking the course. The pre-test scores average 1070 with SD 140, the post-test scores average 1210 with SD 157. is there a significant improvement?
2. Suppose the student above are compared with a sample of 50 students who did not take the course. These student also take the test twice in a 10-week interval. The average improvement(2nd score- 1st score) is 81 point with SD 30 points. The average difference for the group which took the course was 140 with an SD of 60. Does the prep course have a significant effect?