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	Goodman Association Model	Index of Dissimilarity
Field	Sociology	Sociology
Family	Regression model	Process / pipeline
Year of origin	1979	1955
Originator	Leo A. Goodman	Otis Dudley Duncan & Beverly Duncan
Type	Log-multiplicative model for association in ordered contingency tables	Index of evenness of two groups across units
Seminal source	Goodman, L. A. (1979). Simple models for the analysis of association in cross-classifications having ordered categories. Journal of the American Statistical Association, 74(367), 537–552.	Duncan, O. D., & Duncan, B. (1955). A methodological analysis of segregation indexes. American Sociological Review, 20(2), 210–217.
Aliases	RC association model, row-column association model, log-multiplicative model, RC(M) model	dissimilarity index, Duncan index, D index, segregation index
Related	5	5
Summary	Goodman's association models, especially the row-column (RC) model, analyze the association in a two-way contingency table by representing it as a product of estimated scores for the row categories and scores for the column categories, scaled by an intrinsic association parameter. Introduced by Leo Goodman in 1979, they are log-multiplicative rather than purely log-linear, allowing ordered categories to be assigned data-driven scores and the strength of association to be summarized in a single, interpretable coefficient.	The index of dissimilarity, often called the Duncan segregation index, measures how unevenly two groups — such as two racial or occupational groups — are distributed across a set of units like neighborhoods, schools, or occupations. It ranges from 0, when both groups have identical distributions across units, to 1, when the units are completely segregated, and has the intuitive interpretation of the share of one group that would have to relocate to achieve an even distribution.