An electric institute publishes figures on the annual hours of usage of various home appliances. Trash compactors were stated as being used an average of 140 hours per year. However, it is hypothesized that the average usage has increased. To assess this theory, a simple random sample of 36 homes equipped with trash compactors was obtained, and the sample mean usage was 142.4 hours annually. Assume that usage is normally distributed with a population standard deviation of s = 9.2 hours. Is there enough evidence to suggest that trash compactors are used on average more than 140 hours per year?

Let's Do It! 10.8

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