A health psychologist is interested in the potential effect that a change in career focus can have on cardiovascular disease for those in high stress jobs. She chooses to study divorce lawyers (a...

A health psychologist is interested in the potential effect that a change in career focus can have on cardiovascular disease for those in high stress jobs. She chooses to study divorce lawyers (a population that averages a mean systolic blood pressure of 142 with a standard deviation of 13) and measures the blood pressure of 23 former divorce lawyers who switched to environmental law. Those 23 lawyers have a mean systolic blood pressure of 131. If all divorce lawyers switched to environmental law, what would you expect the mean systolic blood pressure to be with 99% confidence?

How much of a margin of error does the health psychologist's study have?