Calculating ROI typically requires some use of estimates and assumptions. For example, we might estimate costs for some parts of the total investment in a program, or make assumptions about missing data. In general, these uncertainties do not cause alarm. In fact, we have several recommendations for using estimates in ROI evaluation. The hallmark of these recommendations: conservatism.
Ensuring a conservative calculation of ROI is a means to an end - credibility is the core issue. An inflated R