For each of the following situations write a model for of the form
where is the number of explanatory variables. Be sure to give the value of and, if necessary, explain how each of the ’s is coded.
583
A model where the explanatory variable is a categorical variable with three possible values.
A model where there are four explanatory variables. One of these is categorical with two possible values; another is categorical with four possible values. Include a term that would model an interaction of the first categorical variable and the third (quantitative) explanatory variable.
A cubic regression, where terms up to and including the third power of an explanatory variable are included in the model.