Question

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 owners' car manuals. She asked a sample of her customers how many times they had their car's oil changed in the last 12 months. The results were (also in attachment): 0, 1, 1, 3, 3, 1, 0, 3, 1, 1, 2, 0, 3, 1, 2. Based on the manager's sample data, and assuming that the frequencies with which all car owners change the oil in their cars per year is normally distributed, what is the estimate of the frequency with which all car owners change the oil in their cars per year, with a confidence level of 99 percent?

Answer 1

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