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 speeders 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 at the same time of day on the same day of the week recording how many miles per hour (mph) each speeder drive over the speed limit. Now let's suppose that he did not obtain equal numbers of speeders under each condition. For illustrative purposes, I have added 3 speeders to the police car condition giving 11 speeders with the police car and 8 speeders with the warning sign. Here are the excess miles per hour driven by the speeders. 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.

Transcribed Image Text:

Excess mph With Police Car Excess mph With Warning Sign 12 18 12 10 4 13 15 19 18 12 10