A 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. a) (17) What is the probability that a randomly selected dentist uses less than 70 ampoules of anesthetics? We are interested in the portion of dentists who use between 70 and 80 ampoules of anesthetic. What percentage of the population is this? sing b) Explain the alue We would like to perform a study on the middle 60% of dentists when classified by anesthetic usage. Find the lower and upper bounds of ampoules to use for this study. c)