A police agency was interested in reducing the speed on a particular stretch of highway. Lore had it that a visible police car with radar was more effective in reducing speed than a warning sign saying that the area is monitored by radar. A police sergeant wondered if the lore was correct, so he tested each method on the same stretch of highway for the same number of hours per day. Now let's suppose that, after catching speeders, the officers also recorded each speeder's prior speeding conviction record, sex, and number of years since obtaining a license. Subjects then were matched on these variables before including them in the study. Data from subjects without a match were discarded from the study (even though they received a speeding citation). Thus, this is a matched-samples design. Here are the excess miles per hour (mph) driven by the speeders from among the matched subjects. Conduct a one-tailed t test at the .05 a level. Does the police car result in lower speeds than the warning sign?
For Information: In Exercise 10 in Module 20 and in Exercise 10 in Module 21

Transcribed Image Text:

Driver Pair No. Excess mph With Police Car Excess mph With Warning Sign 18 12 12 10 4 13 15 19 18 12