The manager of a service station is in the process of analyzing the number of times car owners change the oil in their cars.

The manager of a service station is in the process of analyzing the number of times car owners change the oil in their cars. She believes that the average motorist changes his or her car’s oil less frequently than recommended by the owner’s manual (two times per year). In a preliminary survey she asked 15 car owners how many times they changed their car’s oil in the last 12 months. The results are listed below.1