Hello

We have a data set which includes, for each of 96 cities, 4 estimates

of the number of drug injectors in that city. Each of these estimates

contains error.

We ran a factor analysis to determine their commonality.

We now wish to use the results of this analysis to come up with a

better estimate of the number of drug injectors in each city.

It seems intuitively reasonable to multiply the standardized scoring

coefficients by the estimates, add these together, and then divide by

the sum of the standardized scoring coefficients. I've even seen this

done. But I haven't seen a good proof that this is correct (it may not

be correct!)

Any advice on how to proceed will be appreciated.

Thanks in advance

Peter L. Flom, PhD

Assistant Director, Statistics and Data Analysis Core

Center for Drug Use and HIV Research

National Development and Research Institutes

71 W. 23rd St

New York, NY 10010

(212) 845-4485 (voice)

(917) 438-0894 (fax)