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 α = .05.
e. Group the five intersections on the basis of their mean unused red- light times.

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