114 Income and road rage. The phenomenon of road rage has received much media attention in recent...
Question:
114 Income and road rage. The phenomenon of road rage has received much media attention in recent years. Is a driver’s propensity to engage in road rage related to his or her income? Researchers at Mississippi State University attempted to answer this question by conducting a survey of a representative sample of over 1,000 U.S. adult drivers
( Accident Analysis and Prevention , Vol. 34, 2002). Based on how often each driver engaged in certain road rage behaviors (e.g., making obscene gestures at, tailgating, and thinking about physically hurting another driver), a road rage score was assigned. (Higher scores indicate a greater pattern of road rage behavior.) The drivers were also grouped by annual income: under $30,000, between
$30,000 and $60,000, and over $60,000. The data were subjected to an analysis of variance, with the results summarized in the following table
a. Is a driver’s propensity to engage in road rage related to his or her income?
b. An experimentwise error rate of .01 was used to rank the three means. Give a practical interpretation of this error rate.
c. How many pairwise comparisons are necessary to compare the three means? List them.
d. A multiple-comparisons procedure revealed that the means for the two income groups Between $30 and $60 thousand and Over $60 thousand were not significantly different. All other pairs of means were found to be significantly different. Summarize these results in tabular form.
e. Which of the comparisons of part c will yield a confidence interval that does not contain 0?
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