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# How to test hypotheses of population mean

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Subject: Null/alt hypoth; decision rule; value of test stat; Ho and p-value, interpret
Details: The manufacturer of the X-15 steel belted radial truck tire claims that the mean mileage the tire can be driven before the treads wear out is 60,000 miles. The standard dev of the mileage is 5,000 miles. The C Truck Company bought 48 tires and found the the mean mileage for their trucks is 59,500 miles. Is C Truck Co's experience different from that claimed by the manufacturer at the .05 significance level?

##### Solution Summary

The solution contains detailed explanation of testing whether the population mean is different from a given value.

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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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