Question

the salaries of physicians in a certain speciality are approximately normally distributed. if 25 percent of these physicians earn less than $180,000 and 25 percent earn more than $320,000, approximately what fraction earn

Answer 1

We know P(x<$180,000)=.25 and P(x>$320,000)=.25

Using the formula for normal distributions, we can find the mean and standard deviation (z = (x-mean)/SD) using the given info. Then you'll have two equations with two unknowns.

Finally when finding part a, make sure to do a continuity correction [P(x<$200,000) = P(x≤$200,000.5) = ?]

Explanation: