My knowledge of statistics is pretty sketchy so it didn't come as much of a surprise to be told that the frequently used formula for variance of a sample (divide by n-1, rather than n for a population) is not as unbiased as I had thought. There's a fancy correction factor to take care of this and it uses the gamma function. Unless I am mistaken neither the basic Ti-89 arithmetic system, nor the official Statistics with List Editor flash application have access to the gamma function. Excel only has the incomplete gamma function as GAMMADIST() and, as I've mentioned before, the quality of Excel's statistical methods still sucks. Then I came across this wonderful page with many calculator-compatible approximations for gamma (and probably the clearest explanation of what the function is all about). Thank you Mr. Toth.