In a study of television viewing habits, it is desired to estimate the average number of hours that teenagers spend watching per week. If it is reasonable to assume that σ = 3.2 hours, how large a sample is needed so that it will be possible to assert with 95% confidence that the sample mean is off by less than 20 minutes.
Answer to relevant QuestionsMaking use of the methods of Section 8.7, it can be shown that for a random sample of size n = 2 from the population of Exercise 11.2, the distribution of the sample range is given by Use this result to find c so that R < θ ...Twelve randomly selected mature citrus trees of one variety have a mean height of 13.8 feet with a standard deviation of 1.2 feet, and 15 randomly selected mature citrus trees of another variety have a mean height of 12.9 ...In a random sample of 120 cheerleaders, 54 had suffered moderate to severe damage to their voices. With 90% confidence, what can we say about the maximum error if we use the sample proportion 54/120 = 0.45 as an estimate of ...With reference to Exercise 11.32, construct a 90% confidence interval for the standard deviation of the population sampled, that is, for the percentage of impurities in the given brand of peanut butter. Modify Theorem 11.1 so that it can be used to appraise the maximum error when σ2 is unknown. This method can be used only after the data have been obtained.
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