7. Two Professors taught hypotheses testing by Method 1 for Class 1 and by Method 2 for Class 2, and gave a common exam for both classes. Summary statistics of the exam for both classes are given below. Assuming normality, obtain 95% confidence interval for the difference of the mean exam scores by methods 1 and 2. Is there sufficient evidence to conclude that the Method 1 is more effective at 1% level? Assume that a 2 and -5.

Class 1

Class size (n)

Average score (X

)

24

Class 2

20

85

65