Your prof gave you the equation for the Pearsonian coefficient of skewness (from K. A. Pearson, who introduced the term, as ref'd in Wine, 1964), which is much easier to swallow than the full deal.
the full deal is that the skewness is given by (sum of (x(i) - x-bar)^3/n)/sigma^3 that is to say, it is the third moment of the distribution. whether these two are different, I can't say. I'll bet, nonetheless, that you can make sense of the simpler form more quickly than the full deal. Excel probably works off the third moment calculation. As Dennis said, your second equation is not the same as the first and probably not correct. I'd guess it is missing a pair of parentheses in the numerator. Cheers, Jay Joe wrote: > > I'm taking an undergrad business stat. course. The prof. gave us a formula > to calculate the coefficient of skewness: > > 3(mean - median)/(std. dev ) > > And told us that the formula that excel uses to calculate skewness is > different/wrong. > > I did a little digging to try and understand why Excel would use a > non-standard formula. The only equation that I found which came close to > what my prof. offered up was Pearson's second coef. of skewness which is: > > 3[mean] - [median] / (std. dev.) > > Two questions, is the formula my prof. gave me valid, and why wouldn't I > use the Excel calculation for skewness? Is the formula I was given more > applicable to business statistics than what Excel uses? > > Thanks for helping the statistcally insignificant. > -Joe > > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= -- Jay Warner Principal Scientist Warner Consulting, Inc. 4444 North Green Bay Road Racine, WI 53404-1216 USA Ph: (262) 634-9100 FAX: (262) 681-1133 email: [EMAIL PROTECTED] web: http://www.a2q.com The A2Q Method (tm) -- What do you want to improve today? . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
