We’ve talked repeatedly about using ROI to drive prioritization of requirements based upon value. ROI can be used as the basis for prioritization for all decision making.

If we fail to take risk into account, our calculations will certainly be wrong, and we may make a poor decision. When we talk about accounting for risk in this context, we mean that we are accounting for the unlikely, undesired, or unintentional outcomes. We use the term expected value to refer to the risk adjusted approximation of the outcome. In financial circles, this is also called discounting.

The most common mistake people make when calculating ROI is failing to take into account the expected value of the return or the expected value of the cost of a project.