Dental anxiety study. To gauge their fear of going to a dentist, a random sample of adults completed the Modified Dental Anxiety Scale questionnaire (BMC Oral Health, Vol. 9, 2009). Scores on the scale range from zero (no anxiety)

to 25 (extreme anxiety). The mean score was 11 and the standard deviation was 4. Assume that the distribution of all scores on the Modified Dental Anxiety Scale is approximately normal with m = 11 and s = 4.

a. Suppose you score a 10 on the Modified Dental Anxiety Scale. Find the z-value for your score.

b. Find the probability that someone scores between 10 and 15 on the Modified Dental Anxiety Scale.

c. Find the probability that someone scores above 20 on the Modified Dental Anxiety Scale.