You can use the LMS Test.Lab Data Calculator function in LMS Test.Lab Navigator worksheet.
Put the PSDs functions in the Input Basket by right clicking on data and choosing “Add to input basket”.
Click on “Data Calculator” and press the “Add from Input Basket” button in the data set area.
In the Active Formula Set area, add a formula “AVERAGE” (click on the "f(x)" button to get formulas)
In the “Edit Formula arguments”, enter the following:
F1, F2 and F3 refer to the PSD functions in the Dataset area. It may be necessary to pick “New Function” button to enter all three.
Use the AVERAGE function twice:
Also set the Point id for the resulting calculation by filling in the Point Id field:
Press the “Calculate” button. ‘Average’ will be at F4 and ‘Ave+StdDev’ will be at F5.
Click the “Save Results As” button to store results to the current project.