Question

Solve the problem.

The systolic blood pressures of the patients at a hospital are normally distributed with a mean of 136mm Hg and a standard deviation of 13.8mm Hg Find the two blood pressures having these properties: the mean is midway between them and 90% of all blood pressures are between them.

Answer 1

If 90% are between them, then 5% are to the right and 5% are to the left. Find the z-scores associated with the 5th and 95th percentiles.

Answer 2

Reference http://stattrek.com/probability-distributions/standard-normal.aspx?Tutorial=AP

and http://www.math.unb.ca/~knight/utility/NormTble.htm