Consider an experiment to examine the variation in the effects of different analysts on chemical analyses for the DNA content of plaque (Montgomery 1991). Three female subjects (ages 18–20 years) were chosen for the study. Each subject was allowed to maintain her usual diet, supplemented with 30 mg (15 tablets) of sucrose per day. No toothbrushing or mouthwashing was allowed during the study. At the end of the week, plaque was scraped from the entire dentition of each subject and divided into three samples. The three samples of plaque from each of the subjects were randomly assigned to three analysts chosen at random. They performed an analysis for the DNA content (in micrograms). The data obtained are as follows:

Subject Analyst 1 23

a. Write the appropriate model for the analysis of these data, stating the effect each term used in the model represents and the assumptions made about these effects.

b. Construct an appropriate ANOVA table including appropriate Fstatistics, p-values, and expected mean squares.

c. State the hypothesis of interest for this experiment using the model parameters in part (a). Use the F-statistic and p-value above to make conclusions. Use α = 0.05.