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A researcher studying salaries of police officers around the nation surveyed 64 officers and found a...

A researcher studying salaries of police officers around the nation surveyed 64 officers and found a mean salary of $71,228 with a standard deviation of $9,625. Make a 99% confidence interval for the mean salary of all police officers.

Math   Statistics-And-Probability   
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Answer #1

t critical value at 0.01 level with 63 df = 2.656

99% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

71228 - 2.656 * 9625 / sqrt(64) < < 71228 + 2.656 * 9625 / sqrt(64)

68032.5 < < 74423.5

99% CI Is ( 68032.5 , 74423.5)

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