HomeTechniques and Tips@RISK DistributionsGeometric Mean and Geometric SD in Log-normal

3.27. Geometric Mean and Geometric SD in Log-normal

Applies to: @RISK, all releases

I want to use a log-normal distribution. I have the geometric mean and geometric standard deviation. How can I set up this distribution?

Use RiskLognorm2, but wrap each of the two parameters in a natural-log function. Example:

=RiskLognorm2( LN(2.1), LN(1.8) )

You can type the function directly in Excel's formula bar, or use @RISK's Insert Function button, or use Define Distribution and select Lognorm2 from the Continuous tab.  You can type the LN function right into the boxes in the Define Distribution dialog, as shown in the attached illustration.

Please note: In this application you want Lognorm2, not Lognorm. For the difference between them, please see Entering Parameters for Log-normal Distribution.

Last edited: 2015-06-19


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