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Confidence Level and Sample Size

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A film alliance used a random sample of 50 U.S. citizens to estimate that the typical American spent 78 hours watching videos and DVDs last year. The standard deviation of this sample was 9 hours.

How large a sample should be used to be 90 percent confident the sample mean is within 1.0 hour of the population mean? (Round your answer to the next whole number.)

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  • MSc, Osmania University
  • MSc, Indian Institute of Technology - Roorkee (I.I.T.-ROORKEE)
  • BSc, Banaras Hindu University
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