A simple method for estimating a regression model for κ between a pair of raters |
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Authors: | Stuart R Lipsitz John Williamson Neil Klar Joseph Ibrahim & Michael Parzen |
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Institution: | Medical University of South Carolina, Charleston, USA,;Centers for Disease Control, Atlanta, USA,;Cancer Care Ontario, Toronto, Canada,;Harvard School of Public Health and Dana-Farber Cancer Institute, Boston, USA,;University of Chicago, USA |
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Abstract: | Agreement studies commonly occur in medical research, for example, in the review of X-rays by radiologists, blood tests by a panel of pathologists and the evaluation of psychopathology by a panel of raters. In these studies, often two observers rate the same subject for some characteristic with a discrete number of levels. The κ-coefficient is a popular measure of agreement between the two raters. The κ-coefficient may depend on covariates, i.e. characteristics of the raters and/or the subjects being rated. Our research was motivated by two agreement problems. The first is a study of agreement between a pastor and a co-ordinator of Christian education on whether they feel that the congregation puts enough emphasis on encouraging members to work for social justice (yes versus no). We wish to model the κ-coefficient as a function of covariates such as political orientation (liberal versus conservative) of the pastor and co-ordinator. The second example is a spousal education study, in which we wish to model the κ-coefficient as a function of covariates such as the highest degree of the father of the wife and the father of the husband. We propose a simple method to estimate the regression model for the κ-coefficient, which consists of two logistic (or multinomial logistic) regressions and one linear regression for binary data. The estimates can be easily obtained in any generalized linear model software program. |
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Keywords: | Generalized estimating equations Generalized linear model Measure of agreement |
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