How do you estimate the mean length of plastic sheets?
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A machine cuts plastic into sheets that are 30 feet (360 inches) long. Assume that the population of lengths is normally distributed.
a) The company wants to estimate the mean length the machine is cutting the plastic within 0.25 inch. Determine the minimum sample size required to construct a 90% confidence interval or the population mean. Assume the population standard deviation is 0.50 inch.
N =______ round up to the nearest whole number as needed.
b) Repeat part (a) using an error tolerance o 0.125 inch.
N =______ round up to the nearest whole number as needed
Which error tolerance requires a larger sample size?
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Solution Summary
The solution examines the mean and normal distribution. The error of tolerance required for a larger sample size is determined.
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A machine cuts plastic into sheets that are 30 feet (360 inches) long. Assume that the population o lengths is normally distributed.
a) The company wants to estimate the mean length the machine is cutting the plastic within 0.25 inch. ...
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- BSc , Wuhan Univ. China
- 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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