Jim's systolic blood pressure is a random variable with a mean of 145 mmHg and a standard deviation of 20 mmHg. For Jim's age group, 140 is the threshold for high blood pres- sure.
(a) If Jim's systolic blood pressure is taken at a randomly chosen moment, what is the probability that it will be 135 or less?
(b) 175 or more?
(c) Between 125 and 165?
(d) Discuss the implications of variability for physicians who are trying to identify patients with high blood pressure.