SOLUTION: A manufacturer claims that the life span of its tires is 51000 miles. You work for a consumer protection agency and you are testing these tires. Assume the life spans of the tires

Question 1118002: A manufacturer claims that the life span of its tires is 51000 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 50781 miles. Assume sigma equals 900.
(a) Assuming the manufacturer's claim is correct, what is the probability that the mean of the sample is 50781 miles or less?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
This is a z test for sample means
z=(x-xbar)/sigma/sqrt)(n)
z=(50781-51000)/900/10
z=-219*10/900
z=-2.43
prob=0.0075
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