In a standard dissolution test for tablets for a particular drug product, the manufacturer must obtain the dissolution rate for a batch of tablets prior to release of the batch. Suppose that the dissolution test consists of assays for 24 randomly selected individual 25 mg tablets. For each test, the tablet is suspended in an acid bath and then assayed after 30 minutes. The results of the 24 assays are given here. 19.5 19.7 19.7 20.4 19.2 19.5 19.9 19.2 20.1 19.8 20.4 19.8 19.3 19.7 19.5 20.6 20.4 19.9 19.6 20.8 19.6 19.5 20.0 19.8

a. Does the data appear to be a random sample from a normal distribution?
b. Using a graphical display, determine whether the data appear to be a random sample from a normal distribution.
c. Estimate the mean dissolution rate for the batch of tablets, for both a point estimate and a 99% confidence interval.
d. Is there significant evidence that the batch of pills has a mean dissolution rate less than 20 mg (80% of the labeled amount in the tablets)? Use α = .01.