@Risk: Variable Selection in Tornado Graphs

@RISK uses stepwise regression (F>3.29) to select variables for tornado diagrams; excluded variables fail the F-test threshold.

Jan 21, 2026
Knowledge

Title

Answer

Applies to:
@RISK for Excel 4.x and Up
@RISK for Project 4.x

How does @RISK decide which variables to include when I create a tornado diagram using regression coefficients?

Answer:
@RISK uses stepwise multiple linear regression to select the inputs.

Each variable is tested, and by default it must meet a critical F-value of 3.29 to be included in the regression.
Variables that don’t meet this threshold are excluded from the tornado diagram.

For technical details, see Draper and Smith, Applied Regression Analysis, Wiley, 1966 (“The Stepwise Regression Procedure”).

In practice, the tornado diagram shows the variables that most strongly influence the output according to the regression.

An attached example shows that @RISK’s coefficients may be ordered differently from StatTools, but the numeric values match, since both perform the same regression analysis.

Tornado Graph — How to Set Defaults.

Attachments:
KB145 Financial Forecasting Modified.xlsx

URL Name

variable-selection-in-tornado-graphs