A political scientist developed a questionnaire to determine political tolerance scores (Y) for a random sample of faculty members at her university. She wanted to compare mean scores adjusted for age (X) in each of three categories: full professors, associate professors, and assistant professors. The data results are given in the accompanying tables (the higher the score, the more tolerant the individual).

a. State an ANACOVA regression model that can be used to compare the three groups, controlling for age.
b. What model should be used to check whether the ANACOVA model in part (a) is appropriate? Carry out the appropriate test. Use α = .01.
c. Using ANACOVA, determine adjusted mean tolerance scores for each group, and test whether these adjusted scores differ significantly from one another. Also, compare the adjusted means with the unadjusted means.
[(overall) = 39.667, (group 1) = 4.10, (group 2) = 4.86, and (group 3) = 5.00.]
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