One result is not enough
Every calculator result depends on inputs. Sensitivity analysis asks what happens when an uncertain input changes. The goal is not to predict the future perfectly; it is to understand whether the conclusion is robust or fragile.
Change one important input at a time
Start with the variables you are least sure about: usage, resale value, repair life, energy price, time horizon or recurring fees. Increase and decrease one variable while holding the others steady. This makes it easier to see which assumption is causing the result to move.
Look for a decision flip
If a small change reverses which option costs less, the decision is close. That is useful information. It means the calculator should not present a strong recommendation, and qualitative factors such as reliability, comfort or flexibility may reasonably decide the outcome.
Use ranges instead of invented precision
For uncertain inputs, a low and high estimate can be more honest than one exact figure. If both ends of the range lead to the same conclusion, confidence improves. If the range crosses the break-even point, the result should be described as conditional.
Record the assumptions
A professional comparison is reproducible. Keep the key assumptions visible beside the result so someone can understand why it changed. This is more valuable than a complicated score whose inputs are hidden.
Use this method in a real comparison
Open a reviewed calculator, replace the example inputs with values that fit your situation, then change the assumptions that are most uncertain. A useful result should remain understandable even when the conclusion changes.