# Probability: Systolic Blood Pressure

Assume that the mean systolic blood pressure of normal adults is 120 millimeters of mercury (mm Hg) and the standard deviation is 5.6. Assume the variable is normally distributed.

A.) If an individual is selected at random, find the probability that the person's pressure will be between 118 and 121.8mm Hg.

B.) If a sample of 30 adults is selected at random, find the probability that their mean pressure will be between 118 and 121.8mm Hg.

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#### Solution Preview

Let X be the systolic blood pressure of normal adults. According to hypothesis we know X~N(120,5.6^2).

Since Y=(X-120)/5.6~N(0,1) standard normal distribution, let F(y) be the standard normal distribution function.

Note. F(y)+F(-y)=1

(1) ...

#### Solution Summary

The solution assumes that the mean systolic blood pressure of normal adults is 120 millimeters of mercury (mm Hg) and the standard deviation is 5.6. Assume the variable is normally distributed. Standard normal tables are examined.