| Feature | Expected Monetary Value (EMV) | Actual Outcome |
|---|---|---|
| Nature | Statistical average | Realized financial result |
| Timing | Calculated before the event | Known after the event |
| Purpose | Comparing options under risk | Measuring performance |
Quantitative vs. Qualitative: Decision trees provide a rigorous numerical basis for choices but often fail to capture qualitative factors like brand reputation, employee morale, or ethical considerations.
Revenue vs. Profit: Some diagrams provide gross revenue figures at the end of branches; in these cases, operating costs must be deducted to ensure the comparison is based on net profit.
The Probability Check: Always verify that the probabilities on branches originating from a single circle sum to exactly . If they do not, the calculation will be fundamentally flawed.
Cost Deduction: A common exam error is forgetting to subtract the initial investment cost from the EMV. Always check if the 'Net Gain' is required rather than just the EMV.
Negative Values: Ensure that losses are treated as negative numbers in the summation. Adding a loss instead of subtracting it is a frequent calculation mistake.
Logical Sanity Check: If one option has a much higher probability of success but a lower EMV, double-check the magnitude of the 'failure' loss; high-risk options often have skewed EMVs due to extreme outliers.
The 'Expected' Misconception: Students often think the EMV is the amount the business expects to receive. In reality, the EMV is a statistical mean; the business will likely receive one of the specific outcome values, not the average itself.
Data Reliability: The accuracy of a decision tree is entirely dependent on the quality of the estimates. If probabilities are based on 'gut feeling' rather than market research, the output is unreliable.
Static Nature: Decision trees are snapshots in time. They often fail to account for dynamic external changes, such as a competitor launching a product midway through the implementation of the chosen decision.
