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In order to fairly set flat rates for auto mechanics, a shop foreman needs to estimate the average time it takes to replace a fuel pump in a car. How large a sample must he select if he wants to be 90% confident that the average time is within 20 minutes of the sample average? Assume the standard deviation of all times is 40 minutes.

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Respuesta :

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Answer:

ME = 1.96(45)/sqrt(n) 25 = 1.96(45)/sqrt(n) n = (1.96(45)/25)^2 = 6

Step-by-step explanation:

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