Chapter 7: Problem 18
What condition or conditions must hold true for the sampling distribution of the sample mean to be normal when the sample size is less than \(30 ?\)
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Chapter 7: Problem 18
What condition or conditions must hold true for the sampling distribution of the sample mean to be normal when the sample size is less than \(30 ?\)
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In a large city, \(88 \%\) of the cases of car burglar alarms that go off are false. Let \(\hat{p}\) be the proportion of false alarms in a random sample of 80 cases of car burglar alarms that go off in this city. Calculate the mean and standard deviation of \(\hat{p}\), and describe the shape of its sampling distribution.
A population of \(N=5000\) has \(\sigma=25\). In each of the following cases, which formula will you use to calculate \(\sigma_{\bar{x}}\) and why? Using the appropriate formula, calculate \(\sigma_{\bar{x}}\) for each of these cases. a. \(n=300\) b. \(n=100\)
Let \(x\) be a continuous random variable that has a normal distribution with \(\mu=48\) and \(\sigma=8\). Assuming \(n / N \leq .05\), find the probability that the sample mean, \(\bar{x}\), for a random sample of 16 taken from this population will be a. between \(49.6\) and \(52.2\) b. more than \(45.7\)
In a population of 18,700 subjects, \(30 \%\) possess a certain characteristic. In a sample of 250 subjects selected from this population, \(25 \%\) possess the same characteristic. How many subjects in the population and sample, respectively, possess this characteristic?
The amounts of electricity bills for all households in a city have a skewed probability distribution with a mean of \(\$ 140\) and a standard deviation of \(\$ 30\). Find the probability that the mean amount of electric bills for a random sample of 75 households selected from this city will be a. between \(\$ 132\) and \(\$ 136\) b. within \(\$ 6\) of the population mean c. more than the population mean by at least \(\$ 4\)
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