(Data file: salary gov) For the government salary data described in use the model of obtain tests for the interaction between the indicator for female-dominated occupations and the spline basis for...

(Data file: salary gov) For the government salary data described in use the model of obtain tests for the interaction between the indicator for female-dominated occupations and the spline basis for Score. Obtain a 95% confidence interval for the difference between female-dominated job classes and all other job classes.

(Data file: twins) The data in the file twins give the IQ scores of identical twins, one raised in a foster home, IQ f, and the other raised by birth parents, IQ b. The data were published by Burt (1966), and their authenticity has been questioned. For purposes of this example, the twin pairs can be divided into three social classes C, low, middle, or high, coded in the data file 1, 2, and 3, respectively, according to the social class of the birth parents. Treat IQ f as the response and IQ b as the predictor, with C as a factor. Describe the dependence of the response on the predictors, using appropriate graphs, models discussed in the last chapter, and tests described in this chapter.