On 27 Nov 2002 13:17:52 -0800, [EMAIL PROTECTED] (dennis roberts) wrote: > > > > > > > > > (I don't understand it, but from what I have read I believe the usual > > > technique of simply adding the squares of the SDs is not appropriate > > > because I have (hopefully) correlated data, and different sample > > > sizes) > > > > > this has me puzzled ... how can there be a dependency IN the data IF you > have different samples of different sizes? >
Dennis has pointed to a fatal *flaw* in your question. Do you mean, perhaps, that the groups have means that are extremely different? - in that case (which does, after all, fit one notion that I have of 'correlated data') it would be a bad idea, for most people in most contexts, to present the overall mean and its overall standard deviation. For instance you could have different samples from different people; then you might want to estimate the variance "within-person", or "between person", or both. Those could be useful, for some purposes. Hardly ever would someone want to see the arbitrary combination of multiple, uncontrolled samples. (Unless there is some future use that will use exactly the same Ns....) -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
