From: s_d_lew@my-dejanews.com Subject: Re: Principal Component Analysis Date: Tue, 06 Apr 1999 14:12:49 -0800 Newsgroups: sci.math Keywords: Lay person's description of PCA The way I like to teach eigen-vector/values simplify it to say that it is a way to change the coordinate system so that it is easiest to measure the effects that we are interested in. The eigen values measure the importance of the eigen vector and, the eigen vectors themselves indicate how much of each of the original components contribute to the new "good" coordinate system. Admittedly, this is a pretty gross simplification, but most people understand "change in coordinates". I usually follow it up with my guns-vs-butter economic analogy where the evil professor throws in a bread dimension. I say something like, "Wouldn't it be nice to use the same analysis as guns-vs-butter when we don't have this extra 'bread' dimension." Then I say, "Common sense says a good coordinates for a guns-vs-bread-vs-butter analysis would be something like guns vs (alpha*bread+beta*butter) where alpha and beta tell you how much butter the average person puts on the bread." Then I say something like, "Eigen-vector/value analysis incorporates the information about how much butter the average person puts on bread to select this new coordinate system using alpha and beta." This usually goes on to discuss how this creates eigen value degeneracies, etc, but I usually skip this part for a non-tech audience. I don't know if this is usable in your audience or not, but I thought I'd throw it out there for grins. -slew **** Posted from RemarQ - http://www.remarq.com - Discussions Start Here (tm) ****