134 Dentists’ use of anesthetics. Refer to the Current Allergy &

Clinical Immunology study of the use of local anesthetics in dentistry, presented in Exercise 99 . Recall 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 dentist who used 175 units of local anesthetics in a week.

a. Find the z -score for this measurement.

b. Would you consider the measurement to be an outlier?

Explain.

c. Give several reasons the outlier may have occurred.