[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: RE: matching percentiles technique

From   "Verkuilen, Jay" <>
To   <>
Subject   st: RE: matching percentiles technique
Date   Thu, 25 Jun 2009 12:02:43 -0400

Juanita Riaño wrote:

>I was wondering if any of you have experience working with the "matching percentiles" technique to aggregate indicators with different distributions. I am just using the pctile command for each indicator and then merging the datasets using the resulting percentile distribution. But I am not sure if this is the correct approach.<

The problem has in fact been studied extensively in the psychometrics literature under the name "equipercentile equating." It doesn't work very well as the ECDF is a rather poor estimator of the CDF for this purpose, and the equating curve ends up being rather biased as a consequence. Usually some kind of smoothing of the ECDF is needed to get a good equating curve. This is typically done using kernel smoothing but I'm sure that other methods are possible and may be better in your particular problem. 


Kolen, M.J.  & Brennan, R.L. Test equating, scaling, and linking. Methods and practices, 2nd ed. New York: Springer-Verlag, 2004.

von Davier, A.A., Holland, P.W., & Thayer, D.T. The Kernel Method of Test Equating. New York: Springer-Verlag, 2004.

*   For searches and help try:

© Copyright 1996–2023 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index