Financial advising
(a) Starting with the model in Table 4, add both Em- ployment and Annual Payroll to the model. Does adding this pair improve the fit of the model by a statistically significant amount?
(b) Instead of adding the pair as in (a), add the ratio Annual Payroll/Employment (average payroll salary). Does adding this ratio produce a statistically significant improvement?
(c) Explain your preference among the original model and these two models that add variables.