1. Consider the data from a study reported by Varma and Chilton (1974), that was later re-analyzed by Jones (1980).

This was a simple crossover dental study comparing a test compound to a placebo with regard to their eect on dental hygiene as measured by the change in a dental hygiene index. There were thirty-four patients ran-
domized to the rst group and thirty patients randomized to the second group.

(a) Use proc glm to analyze the data from this experiment.

(b) Is there a dierence of the test compound and placebo with respect to their eect on dental hygiene? If so, which produces the larger change in the index?

(c) Is there any evidence of carryover eect of the test compound?

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Group 1 Group 2 Subject Period 1 Period 2 Period 1 Period 2 Placebo Test Test Placebo 1 0.83 1.83 1.67 0.33 2 1.00 2.17 2.50 0.50 3 0.67 1.67 1.00 -0.17 4 0.50 1.50 1.67 0.50 5 0.50 2.33 1.83 0.50 6 0.83 1.83 0.50 0.33 7 1.00 0.50 1.33 0.67 8 0.67 0.33 1.33 0.00 9 0.67 0.50 0.50 0.17 10 0.33 0.67 2.17 0.83 11 0.00 0.83 1.67 0.33 12 1.17 1.33 1.50 0.00 13 0.00 0.67 1.33 0.50 14 0.50 1.83 1.50 0.50 15 0.33 1.50 1.33 0.00 16 0.33 1.50 0.67 -0.17 17 0.50 1.17 1.67 0.50 18 1.00 1.67 2.50 0.67 19 0.00 1.33 1.83 0.00 20 0.50 1.50 0.83 0.67 21 -0.50 2.83 2.33 0.17 22 0.17 2.33 1.17 0.50 23 1.00 1.33 1.33 0.00 24 1.00 1.67 1.33 0.83 25 1.33 0.67 0.33 1.33 26 0.33 0.83 2.17 1.17 27 2.00 1.00 1.00 0.33 28 4.00 0.17 0.33 1.00 29 0.83 1.67 1.17 0.17 30 0.50 1.33 0.50 0.50 31 0.50 1.50 32 0.50 1.67 33 2.17 1.33 34 0.67 1.17