Question 492974: The U.S. Department of Transportation requires tire manufacturers to provide tire performance information on the sidewall of the tire so that a prospective customer can be better informed when making a purchasing decision. One very important measure of tire performance is the tread wear index, which indicates the tire's resistance to tread wear compared with a tire graded with a base of 100. This means that a tire with a grade of 200 should last twice as long, on average, as a tire graded with a base of 100. Suppose that a consumer organization wants to estimate the actual tread wear index of a brand name of tires graded 200 that are produced by a certain manufacturer. A random sample of 18 of these tires produced a sample mean tread wear index of 195.3 and a sample standard deviation of 21.4. Assuming that the population of tread wear indices is normally distributed, compute a 95% confidence interval estimate for the population mean tread wear index for tires produced by this manufacturer under this brand name. Place your answer, rounded to 2 decimal places
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! This means that a tire with a grade of 200 should last twice as long, on average, as a tire graded with a base of 100.
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Suppose that a consumer organization wants to estimate the actual tread wear index of a brand name of tires graded 200 that are produced by a certain manufacturer.
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A random sample of 18 of these tires produced a sample mean tread wear index of 195.3 and a sample standard deviation of 21.4.
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Assuming that the population of tread wear indices is normally distributed, compute a 95% confidence interval estimate for the population mean tread wear index for tires produced by this manufacturer under this brand name. Place your answer, rounded to 2 decimal places
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p-hat = 195.3
ME = 1.96 = 9.8863
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95% CI: 195.3 - 9.8863 < u < 195.3 + 0.9963
185.41 < u < 205.19
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Cheers,
Stan H.
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