Where there are a range of possible outcomes which can be identified and a probability distribution can be attached to those values.
Process as following:
Step 1 Calculate an expected value of the NPV
Step 2 Measure risk, for example in the following ways.
（a）By calculating the worst possible outcome and its probability.
（b）By calculating the probability of negative NPV.
（c）By calculating the standard deviation of the NPV

Problems with expected values
·The probability estimation is subjective
·Identifying the probabilities of each outcome can be difficult.
·An investment may be one-off, and ‘expected’ NPV may never actually occur.