Why this is mistaken
The mistaken procedure treats rejection as additive: every unselected project, task, and imagined use becomes part of one giant cost. This seems cautious but misstates the choice.
If the resource could have supported only one alternative, selecting the chosen use displaces the next-best feasible use—not all alternatives simultaneously. An option outside the capital limit or decision authority was not available to be sacrificed in that frame.
To diagnose the error, require a ranked feasible set and ask which single option would be selected if the chosen option disappeared. Then ask why each excluded option is either lower-valued or infeasible. This makes the counterfactual explicit.
Where to watch
When this mistake may appear
- A decision prompt lists more than two alternatives.
- An attractive option violates a budget, legal, timing, or capacity constraint.
Check your work
Your work may contain this mistake if:
- Adds the values of all unselected alternatives.
- Selects an infeasible alternative as the opportunity cost.
- Names a forgone option without identifying the scarce resource or decision maker.