SOLUTION: Samsung wants to know how long cell phone owners keep their phones before upgrading. A simple random sample of 23 cell phone owners results in a mean of 2.64 years and a standard

Question 1086335: Samsung wants to know how long cell phone owners keep their phones before upgrading. A simple random sample of 23 cell phone owners results in a mean of 2.64 years and a standard deviation of 0.71 years. Assume the sample is drawn from a normally distributed population.
Find the 95% confidence interval of the population mean.

If you worked for Samsung and decided you wanted to be 99% confident that the sample mean is within 0.25 years of the population mean, how large of a sample would you need to take? Assume that σ=0.71 for this calculation.

Explain why the population parameter may NOT follow a normal distribution. Would you expect the data to show a positive or negative skew? Explain. If the data were not normally distributed, how would this affect the calculations for the confidence interval?

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Samsung wants to know how long cell phone owners keep their phones before upgrading. A simple random sample of 23 cell phone owners results in a mean of 2.64 years and a standard deviation of 0.71 years. Assume the sample is drawn from a normally distributed population.
Find the 95% confidence interval of the population mean.
2.64-1.96*0.71/sqrt(23) < u < 2.64+1.96*0.71/sqrt(23)
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If you worked for Samsung and decided you wanted to be 99% confident that the sample mean is within 0.25 years of the population mean, how large of a sample would you need to take? Assume that σ=0.71 for this calculation.
n = [2.5758*0.71/0.25]^2 = 54 when rounded up
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Explain why the population parameter may NOT follow a normal distribution. Would you expect the data to show a positive or negative skew? Explain. If the data were not normally distributed, how would this affect the calculations for the confidence interval?
Comment:: I'll leave that to you.
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Cheers,
Stan H.
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