1 A group of 10 students was pretested before instruction an

1. A group of 10 students was pretested before instruction and posttested after 6 weeks of instruction with the following achievement scores: (a) For two data sets (Before and After), construct (1) box-plots and (2) mean plots including S.E. (15 points) (b) Is there evidence of an improvement in achievement over this 6-week period? Justify using a paired test. You can solve by hand, or use R or SAS. Use d.f =9 since n-l = 10-1 =9 for a paired test. Use o = 0.05. (15 points)

Solution

box plot for pre and post instruction data

b) H0: There is no improvement in achivement in 6-week period

against

H1: There is improvement in achivement in 6-week period

Paired T for Postested - Pretested

             N   Mean StDev SE Mean
C2          10 15.60   4.38     1.38
C1          10 13.10   4.43     1.40
Difference 10 2.500 2.224    0.703

95% CI for mean difference: (0.909, 4.091)
T-Test of mean difference = 0 (vs not = 0): T-Value = 3.56 P-Value = 0.006

as p-value = 0.006 < 0.05 we conclude that there is evidence of improvement in achivement over this 6-week period