1) In multiple regression analysis, a residual is the difference between the value of an independent variable and its corresponding dependent variable value.
2) A variance inflation factor cannot be computed for a dummy variable
3) An example of a dummy variable is "time to product's first repair" in years.
4) If the hypothesis, Ho: ß1= 0 is rejected, then the sample regression coefficeint b1, indicates the change in the predicted value for a unit change in X1 when all other Xi variables are held constant