Factor analyzing a correlation matrix is SO easy (I am not making this up)
By AnnMaria's Blog on July 02, 2013
When I first went to graduate school in the 1970s (yes, for my MBA, in 1978) , if one were to comment casually, “And then I factor-analyzed the correlation matrix to solve that problem.” Everyone would say, “Ooooh.” Back in those days before statistical calculators (forget the Internet), when computers only came in big (really big) blue boxes and SAS probably was still compiled on punched cards and your department had to pay for computer time, you did it by hand if you were a broke graduate student. Yes, I mean literally with a pencil in your hand. First, you computed the correlations between each of the items and then you applied some equations you can find in any detailed book on factor analysis, which I had forgotten and then looked up again in the documentation here. . . .