Suppose we have a set of blood pressures with a mean of 110 Systolic, and a sample standard deviation of 15 points. If we assume a normal distribution of Systolic blood pressures, then between what two values can we be assured 99.7% of all Systolic blood pressures will lie?

Question

Suppose we have a set of blood pressures with a mean of 110 Systolic, and a sample standard deviation of 15 points.  If we assume a normal distribution of Systolic blood pressures, then between what two values can we be assured 99.7% of all Systolic blood pressures will lie?

PsyDAG · Answer

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.4985) between score and mean to get the Z score. Z = (score ± mean)/SD