Some decision models arIn chapter 9, we ran "The outsourcing model" in Excel using If analysis. is also descriptive in that it simply allows you to evaluate the cost impact of different (_ _). Note that ) is an uncontrollable variable we can vary to evaluate the costs of the decision alternatives. The model itself does not include any decision variables. Descriptive models are used to explain the behavior of systems, to predict future events as inputs to planning processes, and to assist decision makers in making decisions.e descriptive; they simply describe relationships and provide information for evaluation. What are examples of descriptive models; they describe relationships between the dependent and independent variables