Some college professors make bound lecture notes available to their classes in an effort to improve teachinp effectiveness. Marketing Educational Review (Fall 1994)

published a study of business students' opinions of lecture notes. Two groups of students were surveyed86 students enrolled in a promotional strategy class that required the purchase of lecture notes, and 35 students enrolled in a saleslretailing elective that did not offer lecture notes. At the end of the semester, the students were asked to respond to the statement: "Having a copy of the lecture notes was [would be] helpful in understanding the material." Responses were measured on a nine-point semantic difference scale, where 1 = "strongly disagree" and 9 = "strongly agree." A summary of the results are reported in the table.
................................................................................
Classes Buying Classes Not Buying Lecture Notes Lecture Notes ................................................................................
n, = 86 n, = 35 - -
x, = 8.48 x2 = 7.80 s: = 0.94 s; = 2.99 Source: Gray, J. I., and Abernathy, A. M. "Pros and cons of lecture notes and handout packages:

Faculty and student opinions," Murketing Erlucution Review, Vol. 4, No. 3, Fall 1984, p. 25

(Table 4). American Marketing Association.

a. Describe the two populations involved in the comparison.

b. Do the samples provide sufficient evidence to conclude that there is a difference in the mean responses of the two groups of students? Test using a = .01.

c. Construct a 99% confidence interval for (p, - p2).

Interpret the result.

d. Would a 95% confidence interval for (P, - p,) be narrower or wider than the one you found in part c?

Why?