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Under certain specified conditions, ecological data, e.g., the percentage of non-whites and the percentage in domestic service for different community areas, can be used to estimate the "individual correlation" between two dichotomous classifications, e.g., the non-white-white classification and the domestic service-other than domestic service classification. Quite accurate estimates are obtained for some data on the relation between color and occupation, somewhat less accurate estimates on the relation between color and literacy. For some situations where the specific conditions here discribed are not met, other conditions are presented that lead to different methods for estimating the individual correlation from the ecological data. These methods are developed for the study of the individual correlation between two dichotomous variables, between two qualitative variables where one of them is dichotomous, and between two quantitative variables.
Leo A. Goodman (Fri,) studied this question.