Statistics
posted by Sam .
In 2002 John Daly led the PGA tour in driving distance with an average drive of 305.5 yards and a standard deviation of 17.2 yards. Assuming that these distances are normally distributed, 80% of John Daly's drives are longer than what distance?

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the Z score related to that proportion. Insert values in the equation above and solve for the score. 
The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 170 and a variance of 4. The material is considered defective if the breaking strength is less than 166 pounds. What is the probability that a single, randomly selected piece of material will be defective?