Crystal Ball 7.1 Reins in Uncertainty

Its been 10 years since IT gadfly Stan Kelly-Bootle called the PC spreadsheet "the Uzi of creative corporate accounting," but too many decisions are still being made on the basis of point-value estimates at the hopeful end of the error range. Decisioneerings Crystal Ball 7.1, released earlier this spring, eliminates the excuses for getting along without a probabilistic add-in to Microsoft Excel.

The 7.1 updates Extreme Speed option imposes limits on a users uncertainty models. It cant be used when a model spans multiple linked workbooks, although it can handle multiple worksheets in a single workbook file.

There are also restrictions on user-defined functions if Extreme Speed compatibility is desired—but for the majority of models, the option lives up to its name. It accelerated my simple earnings-forecast scenario to run 100,000 trials in just a few seconds.

Setting up an uncertainty model isnt as easy as entering numbers in spreadsheet cells, and models can return ridiculous results if created by a user with no understanding of the implications of certain probability distributions. For example, a user who thinks that normal distributions are commonplace may create a labor-cost model in which some cases have workers paying for the privilege of coming to the office.

Thats what it means when the tails of the bell curve stretch infinitely far in both directions. Log-normal distributions are often the better choice, and Crystal Ball offers them—but you have to know why theyre there.

Crystal Ball is priced starting at $835 and is available in three versions. Extreme Speed is enabled only in the higher-end versions, which are priced starting at $1,795.

More information is at www.decisioneering.com.

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