Question

A manufacturer claims that the life span of its tires is

51,000

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

50,723

miles. Assume

sigmaσequals=800.

Complete parts​ (a) through​ (c).

​(a) Assuming the​ manufacturer's claim is​ correct, what is the probability that the mean of the sample is

50 comma 72350,723

miles or​ less?

nothing

​(Round to four decimal places as​ needed.)

Answer 1

a) Assuming the manufacturer's claim is correct.

Mean = = 51000

Standard deviation = = 800

Sample size = 100

We have to find P( 50723)

For finding this probability we have to find z score.

That is we have to find P(Z - 3.46)

P(Z - 3.46) = 0.0003