Protocol

Rank assumptions by decision leverage

Not every uncertain number deserves equal research budget.

When it fits

A model contains many uncertain inputs and the team does not know which ones deserve analysis or evidence.

When to avoid it

Tornado-style rankings depend on chosen ranges and one-at-a-time variation; correlated inputs can change the ordering.

Why it matters

Vary each important input across its plausible range and record the resulting change in decision value. Rank the inputs by the size of that effect. Investigate the high-leverage assumptions first, especially when their ranges can cross a decision threshold.

Steps

Each input uses a defensible range rather than an arbitrary percentage.
The same outcome/value measure is used for comparison.
Inputs are ranked by impact on the decision, not by how uncertain they feel.
Decision-flipping inputs are flagged separately from inputs that only change totals.
Correlated inputs are noted for later joint analysis.

An example

A cost model may show that implementation time matters far more than license price even though license price gets most of the discussion.

Check your result

The next analysis or data-collection task targets an assumption capable of changing the decision.

Keep this limit in mind

Tornado-style rankings depend on chosen ranges and one-at-a-time variation; correlated inputs can change the ordering.

Connected ideas

Evidence and sources

Supports

The 2025 decision-analysis handbook presents tornado diagrams as a way to display which inputs drive the largest changes in deterministic model value.

The ranking depends on the ranges chosen for each input, so implausible ranges can create misleading importance.

Perform Deterministic Analysis and Develop Insights · Tornado diagram for deterministic sensitivity analysis

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Perform Deterministic Analysis and Develop Insights