SOLUTION: The breaking strength (in pounds) of a certain new synthetic is normally distributed with a mean of 174 and a variance of 9. The material is considered defective if the breaking st

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Question 616853: The breaking strength (in pounds) of a certain new synthetic is normally distributed with a mean of 174 and a variance of 9. The material is considered defective if the breaking strength is less than 168 pounds. What is the probability that a single, randomly selected piece of material will be defective. Give the answer to two decimal places. Could someone please explain this to me step by step.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi, 

The breaking strength (in pounds) of a certain new synthetic is normally distributed 

with a mean of 174 and a variance of 9. 

P(defective) = P( z < (168-174)/9) = P(z < -2/3) NORMSDIST(-.6667) = .25

P(defective)= .25