posted by Andrew .
The breaking strength (in pounds) of a certain new synthetic is normally distributed with a mean of 175 and a variance of 4. The material is considered defective if the breaking strength is less than 170 pounds. What is the probability that a single, randomly selected piece of material will be defective. Give the answer to four decimal places.
Z = (score-mean)/SD
SD = √variance
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.