Applies to: @RISK 4.x and Up

How to make sum of distributions equal fixed value

Answer:
Use scaling helper cells.

Let the original distributions vary freely. Then create helper cells that rescale them so their sum equals the desired total. Each helper cell equals:

(original distribution × desired total) ÷ actual total of all distributions

Because every helper cell is scaled by the same factor, the helper cells will always add up exactly to the desired value.

Use the helper cells (not the original distributions) in all your model formulas. If needed, mark the helper cells as @RISK outputs to record their values during simulation.

This method works for continuous distributions. For discrete distributions, a different approach is required (for example, multinomial-style modeling).

 

Attachments:
KB0041_FixedTotalOfDistributions.xlsx