The weight of many manufactured items is approximately normally distributed. For new U.S. pennies, the mean is 3.11 grams and the standard deviation is 0.05 gram (Youden, 1962).
a. What proportion of all new pennies would you expect to weigh more than 3.20 grams?
b. What weights separate the middle 80 percent of the pennies from the lightest 10 percent and the heaviest 10 percent?