On Fri, 27 Feb 2004 08:13:09 -0500, Bruce Weaver <[EMAIL PROTECTED]> wrote: [ ... ] > > We must be thinking about different formulae. I was > referring to this computational formula for the sum of > squared deviations about the mean (SS): > > > SS = sum[X^2] - (sum[X])^2/n >
That *is* the formula with the bad reputation. It should not be used as a computational formula for computers -- unless there is some degree of protection against 'bad data'. It works okay for a lot of simple datasets; it only fails on occasional sets of 'real' data. The person who wrote the program generally knows to subtract off your huge constants; that can be protection, too. But I've seen someone use a stat-pack 'date' variable in regression, to control for 'week' -- when the dates were internally held as the time since some 19th century zero-point, as measured in seconds or maybe milliseconds. I don't want my stat-pack to blow up for that, -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html "Taxes are the price we pay for civilization." . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
