31.10 Analyzing correlated variables

Perfect positive or negative correlations between pairs of variables can be specified, for use during sensitivity analysis. These value linkages are set up in the Variables View, Sensitivity Analysis Tab as described in section: Sensitivity Analysis Correlations.

Once created, the correlation is identified in the properties of both variables. Thus, when you choose to perform a sensitivity analysis on either member of a correlated pair of variables, TreeAge Pro will auto-adjust the correlated variable at the same time.

To perform a sensitivity analysis using correlated variables:

• Open the Special Features tutorial example tree, Correlated Variables. This tree already includes a positive correlation specified between the variables utilLoseFoot and utilLoseLeg. See figure above.

• Select the root, decision node.

• Choose Analysis > Sensitivity Analysis > One-Way… from the menu.

• In the Sensitivity Analysis dialog, select the variable utilLoseFoot. Specify 10 intervals and a range of 0.4 to 0.9. Click OK.

As the selected variable utilLoseFoot moves within its range (0.4 to 0.9), the correlated variable utilLoseLeg will move within its range (0.3 to 0.7).

Note that the Treat Foot strategy's EV rises with the value of utilLoseFoot even though utilLoseFoot is not referenced by that strategy. This change is a result of the change in the correlated variable utilLoseLeg.