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

A.) If an individual is selected at random, find the probabilitythat 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.

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

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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.