Validity of Data A lack of “good, clean data” means that whatever data are available must often be distilled and manipulated (we call it “fudging”) before being used in a model. Unfortunately, the validity of the results of a model is no better than the validity of the data that go into the model. You cannot blame a manager for resisting a model’s “scientific” results when he or she knows that questionable data were used as input. This highlights the importance of the analyst understanding other business functions so that good data can be found and evaluated by the analyst. It also emphasizes the importance of sensitivity analysis’ which is used to determine the impact of minor changes in input data. Some solutions are very robust and would not change at all for certain certain changes in the input data.