Question

Using the Empirical rule to answer. Systolic blood pressure for adult men are normally distributed with a mean of 120 and a standard deviation of 8. The middle 68% of adult men have systolic blood pressure readings that fall between what two numbers-?

Answer 1

middle 68% means (100-68)% =32% divided into left and right tail.

32% /2 = 16% in left tail and 16% in right tail

Z cutoff value for left tail area under standard normal curve is -0.99.............by using =NORMSINV(0.16) or Z table

Z cutoff value for right tail area under standard normal curve is 0.99...................by using =NORMSINV(1-0.16) or Z table.

Therefore,

and

The middle 68% of adult men have systolic blood pressure readings that fall between 112 and 128