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# Random Sampling of Defective Products

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A quality inspector is interested in the time spent replacing defective parts in one of the company's products. The average time spent should be at most 20 minutes per day according to company standards.

To conduct the test, a random sample of 36 employees is chosen. The average time spent replacing defective parts for the sample was 20.5 minutes with a sample variance of 16 minutes.

Perform the test at a 5% level of significance. State the hypotheses to be tested, the decision rule, the test statistic, and your decision.

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The solution assists with performing the test at a 5% level of significance to the random sample of employees chosen.

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A quality inspector is interested in the time spent replacing defective parts in one of the company's products. The average time spent should be at most 20 minutes per day according to company standards.

To conduct the test, a random sample of 36 employees is chosen. The average ...

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###### Education
• 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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