The Tornado Chart tool measures the impact of each model variable one at a time on a target forecast. The tool displays the results in two ways, described in these sections:

This method differs from the correlation-based sensitivity method built into Crystal Ball because this tool tests each assumption, decision variable, precedent, or cell independently. While analyzing one variable, the tool freezes the other variables at their base values. This measures the effect of each variable on the forecast cell while removing the effects of the other variables. This method is also known as "one-at-a-time perturbation" or "parametric analysis."

The Tornado Chart tool is useful for:

Measuring the sensitivity of variables that you have defined in Crystal Ball.

Quickly pre-screening the variables in your model to determine which ones are good candidates to define as assumptions or decision variables. You can do this by testing the precedent variables of any formula cell. See for more information on precedents.

The following sections describe how to create and use tornado charts and spider charts: