posted by Anonymous .
The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 173 and a variance of 9. The material is considered defective if the breaking strength is less than 167 pounds. What is the probability that a single, randomly selected piece of material will be defective?
Z = (score-mean)/SD
variance = √SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.