Refer to Exercise 15.41. Based on a residuals analysis, do the necessary conditions for conducting the test of hypotheses appear to be valid?

Exercise 15.41

Refer to Exercise 15.40.

a. What was the relative efficiency of the period of day factor in the analysis of the data in Exercise 15.40?

b. What was the relative efficiency of the intersection factor in the analysis of the data in Exercise 15.40?

c. In future traffic studies, would you recommend including factors to control for the variation in intersection and/or period of day?

Exercise 15.40

Mason, Gunst, and Hess (2003) describe the following study. A traffic engineer designs a study to compare the total unused red-light times for five methods of traffic-light signaling (A, B, C, D, and E). The engineer randomly selects five intersections in a major city and five time periods spaced across the day. The following table contains the unused red-light time in minutes, with the letter in parentheses indicating the method of signaling.

a. Identify the design by name.

b. Write a model for this study, identifying all the terms in the model.

c. Describe how randomization could be conducted in this study.

d. Is there significant evidence of a difference in the mean unused red-light times for the five signaling methods? Use a  .05.

e. Group the five intersections on the basis of their mean unused red-light times.