. For each of the following situations write a model for Î¼y of the form Î¼y = Î²0 + Î²1x1 + Î²2x2 +Â· Â· Â·+Î²px p where p is the number of explanatory variables. Be sure to give the value of p and, if necessary, explain how each of the xâ€™s is coded.
(a) A model where the explanatory variable is a categorical variable with four possible values.
(b) A model where there are three 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.
(c) A quartic regression, where terms up to and including the fourth power of an explanatory variable are included in the