The prevalence of the Flaw of Averages is due to the fact that millions of spreadsheet users plug their best guesses of uncertain numbers into their models, naively believing that they are getting the best outputs. However, the Strong Form of the Flaw of Averages isn’t news to mathematicians. They have known it for over a century as **JENSEN’S INEQUALITY**. Of course, with a name like that, no wonder no one else has heard of it.

A mathematician, by the way, would refer to a typical spreadsheet model with inputs, outputs, and formulas connecting them as a FUNCTION. And if some of the inputs were uncertain numbers, a mathematician would call it a FUNCTION OF RANDOM VARIABLES.

Therefore, the millions of spreadsheet models in the world with uncertain inputs are actually **FUNCTIONS OF RANDOM VARIABLES.** So if you use spreadsheets, ...

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