The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 125 and a variance of 25. The material is considered defective if the breaking strength is less than 113.5 pounds. What is the probability that a single, randomly selected piece of material will be defective?

Answer 1

Z = (score-mean)/SD

Variance = SD^2

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.