SOLUTION: the average life of a brand of automobile tires is 30,000 miles with a standard deviation of 2,000 miles. If a Tire is randomly selected and tested find the probability that it wil

Algebra ->  Linear-equations -> SOLUTION: the average life of a brand of automobile tires is 30,000 miles with a standard deviation of 2,000 miles. If a Tire is randomly selected and tested find the probability that it wil      Log On


   

Question 324334: the average life of a brand of automobile tires is 30,000 miles with a standard deviation of 2,000 miles. If a Tire is randomly selected and tested find the probability that it will have a life span between 25,000 and 28,000 miles. Assome the variable is normally distributed
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Find the z scores for 25000 and 28000.
z1=%28x-mu%29%2Fsigma=%2825000-30000%29%2F2000=-2.5
z2=%28x-mu%29%2Fsigma=%2828000-30000%29%2F2000=-1.0
Find the corresponding P(z).
P%28z1%29=0.00621
P%28z2%29=0.15866
Subtract the probabilities to find the probability for the range,
(25000%3C=x%3C=28000)
P%28x%29=0.15866-0.00621=0.1524