math
posted by Anonymous .
The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 165 and a variance of 4. The material is considered defective if the breaking strength is less than 161 pounds. What is the probability that a single, randomly selected piece of material will be defective

Z = (scoremean)/SD
Variance = SD^2
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.