A psychologist has devised a stress test for dental patients sitting

in the waiting rooms. According to this test, the stress scores (on a scale of 1 to

10) for patients waiting for root canal treatments are found to be approximately

normally distributed with a mean of 7.59 and a standard deviation of 0.73.

a) What percentage of such patients have a stress score lower than 6.0?

b) What is the probability that a randomly selected root canal patient sitting in the

waiting room has a stress score between 7.0 and 8.0?

c) The psychologist suggests that any patient with a stress score of 9.0 or higher

should be given a sedative prior to treatment. What percentage of patients

waiting for root canal treatments would need a sedative if this suggestion is

accepted?