Chapter 7: Problem 53
According to the central limit theorem, the sampling distribution of \(\hat{p}\) is approximately normal when the sample is large. What is considered a large sample in the case of the proportion? Briefly explain.
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Chapter 7: Problem 53
According to the central limit theorem, the sampling distribution of \(\hat{p}\) is approximately normal when the sample is large. What is considered a large sample in the case of the proportion? Briefly explain.
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According to the American Time Use Survey results released by the Bureau of Labor Statistics on June 24,2015, Americans age 15 and over watched television for an average of 168 minutes per day. Suppose that the current distribution of times spent watching television per day by all Americans age 15 and over has a mean of 168 minutes and a standard deviation of 20 minutes. Find the probability that the average time spent per day watching television by a random sample of 400 Americans age 15 and over is a. \(165.70\) to 167 minutes b. more than \(169.8\) minutes c. at most 163 minutes
In a January 2014 survey conducted by the Associated PressWe TV, \(68 \%\) of American adults said that owning a home is the most important thing or \(a\) very important but not the most important thing (opportunityagenda.org). Assume that this percentage is true for the current population of American adults. Let \(\hat{p}\) be the proportion in a random sample of 1000 American adults who hold the above opinion. Find the mean and standard deviation of the sampling distribution of \(\hat{p}\) and describe its shape.
What is an estimator? When is an estimator unbiased? Is the sample mean, \(\bar{x}\), an unbiased estimator of \(\mu\) ? Explain.
The amounts of electricity bills for all households in a particular city have an approximate normal distribution with a mean of \(\$ 140\) and a standard deviation of \(\$ 30\). Let \(\bar{x}\) be the mean amount of electricity bills for a random sample of 25 households selected from this city. Find the mean and standard deviation of \(\bar{x}\), and comment on the shape of its sampling distribution.
The package of Ecosmart Led 75 -watt replacement bulbs that use only 14 watts claims that these bulbs have an average life of 24,966 hours. Assume that the lives of all such bulbs have an approximate normal distribution with a mean of 24,966 hours and a standard deviation of 2000 hours. Let \(\bar{x}\) be the average life of 25 randomly selected such bulbs. Find the mean and standard deviation of \(\bar{x}\), and comment on the shape of its sampling distribution.
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