Question

For males in a certain town, the systolic blood pressure is normally distributed with a mean of 120 and a standard deviation of 9. Using the empirical rule, determine the interval of systolic blood pressures that represent the middle 68% of males.

Answer 1

Empirical rule: about 68% of values lie within ±1 standard deviation of the mean.
Mean ± 1 SD = 120 ± 9 → interval = [111, 129] mm Hg.