Question

The systolic blood pressure X of adults in a region is normally distributed with mean 112 mm Hg and standard deviation 15 mm Hg.

A person is considered “prehypertensive” if his systolic blood pressure is between 120 and 130 mm Hg.

Find the probability that the blood pressure of a randomly selected person is prehypertensive.

Answer 1

Given:

= 112 mm Hg, = 15 mm Hg

Let X denote the systolic blood pressure of adults

Find: P(120 < X < 130)

Calculation:

P(120 < X < 130) = P(0.53 < Z < 1.2)

P(120 < X < 130) = P(Z < 1.2) - P(Z < 0.53)

P(120 < X < 130) = 0.8849 - 0.7031 ..................From standard Normal table.

P(120 < X < 130) = 0.1818

0.1818 is the probability that the blood pressure of a randomly selected person is hypertensive.