Serum cholesterol is related to age & sex, investigators prefer to express this as z-scores. If X = raw serum cholesterol, then z= x-u/sigma, where u is the mean & sigma is the standard deviation of serum cholesterol for a given age-gender group. Suppose Z is regarded as a standard normal random variable. A person is regarded as having high cholesterol if Z > 2.0 and borderline cholesterol if 1.5 < Z < 2.0. What proportion of people have borderline cholesterol?