12. The principal of a school wanted to see how the SAT scores compared when given two different programske an SAT class during the school day every other day and Group 2 was assigned to a local prep class on
study. A total of 18 students were randomly assigned to two equal sized groups. Group I was assigned to take
Saturdays. The final SAT scores for each group are shown in the table below. What inference can be made
about the results?
Group 1
Group 2
580
610
590
540
490
510
520
560
580
540
450
560
430
530
530
500
520
470
Mean: 553
Mean: 503
(a) Calculate Xz - X2. [2 points]