A statistics professor is about to select a statistical software package for her course. One of the most important features, according to the professor, is the ease with which students learn to use the software. She has narrowed the selection to two possibilities: software A, a menu-driven statistical package with some high-powered techniques, and software B, a spreadsheet that has the capability of performing most techniques. To help make her decision, she asks 40 statistics students selected at random to choose one of the two packages. She gives each student a statistics problem to solve by computer and the appropriate manual.

The amount of time (in minutes) each student needed to complete the assignment was recorded.

a. Can the professor conclude from these data that the two software packages differ in the amount of time needed to learn how to use them? (Use a 1% significance level.)

b. Estimate with 95% confidence the difference in the mean amount of time needed to learn to use the two packages.

c. What are the required conditions for the techniques used in parts (a) and (b)?

d. Check to see whether the required conditions are satisfied.