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# Statistics and Confidence Intervals

John Kim is the purchasing manager for your computer, Inc., a manufacture of network servers. A truckload of sheet metal has just arrived. Previous experience with the supplier suggests that the thickness of the sheet metal follows a normal distribution. A random sample of 23 sheets yields an average thickness of 0.192 inches with a standard deviation of 0.0187 inches.

a) Determine the degrees of freedom to be used in further analysis.
b) What is the point estimate that John uses for the thickness of a sheet?
c) Calculate a 95% confidence interval for the population mean for sheet metal thickness.
d) Calculate a 90% confidence interval for the population mean for sheet metal thickness.
e) This shipment will be used to fill an order for NASA to be used in the Space Station project. Their inspectors will be very concerned if the thickness of the sheets does not meet the specifications of 0.20 inches because of the weight calculations that need to be made for the project. Should John accept the shipment? Explain your reasoning clearly.

#### Solution Preview

Please see the attached file. I hope it helps.

John Kim is the purchasing manager for your computer, Inc., a manufacture of network servers. A truckload of sheet metal has just arrived. Previous experience with the supplier suggests that the thickness of the sheet metal follows a normal distribution. A random sample of 23 sheets yields an average thickness of 0.192 inches with a standard deviation of 0.0187 inches.

a) Determine the degrees of freedom to be used in ...

#### Solution Summary

Statistics and confidence intervals are examined. Point estimates shipments are determined

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