How average is an "average user"?

Very often, you will hear software designers talking about "average users". In fact, many of them speak of an "average user" and think of a "dumb user". With this assumption, they lose many users at the high end of the curve...

It makes sense to take the really average user, take a certain confidence interval and make sure that both "pretty naive" and "pretty advanced" users will be able to use your software. However, there's also a limitation on the high end of the curve. As much as a "dumb" user will be confused by too many options or complicated operations, a "geek" user will be annoyed because the software will pretend to know what he wants to do better than he does. Advanced users often have a particular and complex use case scenario in mind. If the software is over-simplified, you'll probably end up losing them, just as much as you'll lose the naive users if the software is too complex.

In a few words, if you ask yourself "could my grandmother use this?", make sure it's not something that only your grandmother would use.