Hi,
It's not scaling, exactly; it's more closely related to kurtosis (peakedness). Have a look at
[
en.wikipedia.org]
Basically in the PERT distribution, this is a way to get fatter or narrower tails, if desired. It's much easier to understand if you experiment with it; we have a trial version you can use for 30 days, so I encourage you to download it and try it out.
Make sure you download the Pro version, though, the PERT function is only in that version.
Cheers,
Alex Edwards
alex@riskamp.com