A manufacturer claims that the life span of its tires is 49,000 miles. You work

Question

A manufacturer claims that the life span of its tires is 49,000 miles. You work for a consumer protection agency and you are testing these tires. Assume the life spans of the tires are normally distributed. You select 100 tires at random and test them. The mean life span is 48,787 miles. Assume =700. Complete parts (a) through (c) (a) Assuming the manufacturer's claim is correct, what is the probability that the mean of the sample is 48,787 miles or less? (Round to four decimal places as needed.) b) Using your answer from part (a), what do you think of the manufacturer's claim? The claim is because the sample me I be considered unusual since it 1 within the range of a usual event, namely within of the mean of the sample means. (c) Assuming the manufacturer's claim is true, would it be unusual to have an individual tire with a life span of 48,787 miles? Why or why not? because 48,787 within the range of a usual event, namely within of the mean for an individual tire

Explanation / Answer

solution=

z=(sample mean-postulated mean) divided by sigma/ sqrt (n)
This is

z=(48,787-49,000)/700/sqrt(100)

z=-213/700/10=-2440/700=-3.043
Probability z <-3.043 is 0.0012

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