Two groups of students were surveyed about lecture notes

Two groups of students were surveyed about lecture notes. One group consisted of 86 students from a promotional strategy class that were required to purchase the lecture notes. The other group consisted of 35 students in a sales/retailing class which didn't offer lecture notes. At the end of the semester, students in both classes were asked if Having a copy of the lecture was (would be) helpful in understanding the material.

The question was measured on a 9 point scale where 1 = strongly disagree and 9 = strongly agree. Descriptive statistics of the rating of the two groups are shown in the following table:

a. Does the data provide sufficient evidence that there is a difference in mean responses of the two groups. Assume α = .01.

b. Construct the 99% confidence interval for the differences in mean. Does the confidence interval support the hypothesis testing conclusion? Explain.