37 Dentists’ use of anesthetics. Current Allergy & Clinical Immunology (March 2004) did a study of allergic reactions of dental patients to local anesthetics. The study reported that the mean number of units (ampoules) of local anesthetics used per week by dentists was 79, with a standard deviation of 23. Consider a random sample of 100 dentists, and let x represent the mean number of units of local anesthetic used per week for the sample.

a. What is mx ?

b. What is sx ?

c. Describe the shape of the sampling distribution of x.

d. Find the z -score for the value x = 80 ampoules .

e. Find P(x 7 80).