Question: For each of the following research questions, specify whether the parameter of interest is one population mean, the population mean of paired differences, or the difference between the means of two populations.
a. Residents of a neighborhood have been complaining about speeding cars. The speed limit in the area is 25 miles per hour. The local police monitor the situation by recording the speed of 100 randomly selected cars. They want to know whether the mean speed of all cars that drive through the area is higher than 25 miles per hour.
b. Refer to part (a). After collecting the data described in part (a), the police decide to install an electronic roadside sign that shows cars how fast they are driving. They then record the driving speed of another 100 randomly selected cars. They want to know whether the mean speed is lower after installation of the sign than it was beforehand.