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Statistics and Confidence Intervals

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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.

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

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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 ...

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  • MA, Shandong Univ.
Recent Feedback
  • "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
  • "excellent work"
  • "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
  • "Thank you"
  • "Thank you very much for your valuable time and assistance!"
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