One feature of a user-friendly computer interface is a stacked menu display. Each time a menu item is selected, a submenu is displayed partially over the parent menu, thus creating a series of “stacked” menus. The Special Interest Group on Computer Human Interaction Bulletin (July 1993) reported on a study to determine the effects of the presence or absence of a stacked menu structure on search time. Twenty-two subjects were randomly placed into one of two groups, and each was asked to search a menu-driven software package for a particular item. In the experimental group (n₁ = 11 ), the stacked menu format was used; in the control group (n₂ = 11), only the current menu was displayed.

a. The researcher’s initial hypothesis is that the mean time required to find a target item does not differ for the two menu displays. Describe the statistical method appropriate for testing this hypothesis.

b. What assumptions are required for inferences derived from the analysis to be valid?

c. The mean search times for the two groups were 11.02 seconds and 11.07 seconds, respectively. Is this enough information to conduct the test? Explain.
d. The observed significance level for the test, part a, exceeds .10. Interpret this result.