Sensitivity analysis
Varies the inputs to a financial model to see which ones actually move the answer. Usually two do and the rest are decoration.
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What it is
Systematic variation of a financial model's inputs to establish which ones actually determine the outcome. Most models have twenty inputs and two that matter, and knowing which two changes both the decision and what you monitor afterwards.
- Input ranges
- A plausible high and low for each variable, grounded in history or evidence rather than in optimism and pessimism.
- One-at-a-time analysis
- Moving each input across its range with others held at base, to rank variables by their influence on the result.
- Break-even points
- The value at which each critical input stops the case working. More useful than any percentage sensitivity, because it is a number you can watch for.
- Combined scenarios
- Several important variables moving together, since real downside cases are correlated rather than independent.
- Monitoring linkage
- The critical inputs carried into the indicator set, so the model's assumptions are actually tracked after approval.
How you run it
- List the inputs and give each an honest rangeNot best case and worst case — plausible high and low, based on history or evidence.
- Vary one at a time firstHold everything else at base and move each input across its range. This ranks the variables by influence, which is the main output.
- Find the break-even on the critical onesAt what value of this input does the case stop working? That number is far more useful than a percentage swing.
- Then vary the important ones togetherReal downside cases involve several things going wrong at once, and they correlate more than models assume.
- Carry the critical inputs into monitoringThe two variables that drive the answer should appear in your leading indicators. That connection is the point of doing this.
The prompt
Run this tool in your own Claude
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Your playbook
It lands in the earliest stage this tool suits. Move it on the Playbook page.
You’ll need
- A working financial model
- A plausible range for each key input
- Someone who will accept an unwelcome result
You’ll end up with
- The variables ranked by influence on the outcome
- Break-even points on the critical ones
- The two inputs that need monitoring