Question

For males in a certain town, the systolic blood pressure is normally distributed with a mean of 135 and a standard deviation of 5. Using the empirical rule, determine the interval of systolic blood pressures that represent the middle 99.7% of males.

Answer 1

Empirical rule: ~99.7% of values lie within ±3 standard deviations of the mean.

Here σ = 5, so 3σ = 15.
Interval = 135 ± 15 = [120, 150] mm Hg.

Thus the middle 99.7% of male systolic BPs are approximately 120–150 mm Hg.