COBOT: Conditional Ordinal-By-Ordinal Test

URL of this page:

We developed a method for testing for association between two ordinal variables, Y and X, while adjusting for covariates Z. The data analysis program ( COBOT-analysis.r) is written in R ( The main analysis functions are COBOT.emp() and COBOT.scores() for calculating empirical and asymptotic p-values when proportional odds models are used to model P(Y|Z) and P(X|Z). Please see the beginning lines of the file for detailed descriptions.

Version history

12/06/2010: Old version did not work for ordinal variables with 3 levels. The new version should work.

12/04/2011: The R Design package has been replaced by R rms package. The code is updated to reflect the change.

07/23/2012: a bug fix in the ifelse() calls inside function COBOT.scores().

Simulation code and other simulation results

Our simulation code is in COBOT-simulation.r.

Other simulation results not included in the article: ordinal-otherresults.pdf

Software package

The code given above has now been incorporated into an R package, PResiduals. This package is freely available at

Contact and paper

For questions, please contact or .

The paper that describes the method is:

Li C, Shepherd BE (2010) Test of association between two ordinal variables while adjusting for covariates. Journal of the American Statistical Association 105:612-620

Topic revision: r14 - 02 Oct 2019, BryanShepherd

This site is powered by FoswikiCopyright © 2013-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Vanderbilt Biostatistics Wiki? Send feedback