If the mean score on an exam in a large class is 75 and the
     If the mean score on an exam in a large class is 75, and the standard deviation is 5, what fraction A  ¢ below 68? Assume the distribution is Normal.  If the mean of a normal distribution is 50in, with a standard deviation of 2, what fraction of the  Suppose that the heights of a population have a mean of 68in, and a sd of 2.5in. What fraction of between 69 and 72 inches? 
  
  Solution
3) mean = 68 std dev = 2.5

