SOLUTION: Many college graduates who are employed full-time have longer than 40 -hour work weeks. Suppose that we wish to estimate the mean number of hours, , worked per week by college grad

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Question 339021: Many college graduates who are employed full-time have longer than 40 -hour work weeks. Suppose that we wish to estimate the mean number of hours, , worked per week by college graduates employed full-time. We'll choose a random sample of college graduates employed full-time and use the mean of this sample to estimate. Assuming that the standard deviation of the number of hours worked by college graduates is 6.20 hours per week, what is the minimum sample size needed in order for us to be 90% confident that our estimate is within 1.2 hours per week of ?
Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Assuming that the standard deviation of the number of hours worked by college graduates is 6.20 hours per week, what is the minimum sample size needed in order for us to be 90% confident that our estimate is within 1.2 hours per week of ?
Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements
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n = [zs/E]^2
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n = [invNorm(0.95)*6.2/1.2]^2
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n = [1.645*6.2/1.2]^2
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n = 73 when rounded up to the nearest whole number
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Cheers,
Stan H.