The systolic blood pressures of the patients at a hospital are normally distributed with a mean of
136 mm Hg and a standard deviation of 13.4 mm Hg. Find the two blood pressures having these
properties: the mean is midway between them and 90% of all blood pressures are between them.
statistics - PsyDAG, Monday, October 12, 2009 at 2:05pm
Looking up under the table of "areas under the normal distribution" for ±.05 in the smaller area, 90% of the scores in a normal distribution fall within the mean ± 1.645 SD.
You should be able to do the calculations.