Parametric Collapsibility and the Lack of Moderating Effects in Contingency Tables with a Dichotomous Response Variable
研究了二分响应变量列联表中优势比和相对风险的可压缩性条件，发现相对风险在影响变量边际分布独立时可压缩，并据此推导出调节效应缺失的条件。
SUMMARY We consider contingency tables having one variable specified as a response with just two categories. We look at conditions for collapsibility of a symmetric and a directed measure of association, the odds-ratio and the relative risk: situations are discussed under which equal partial associations coincide with the corresponding marginal association. Contrary to the odds-ratio the relative risk is collapsible, if there are independencies in the marginal distribution of the influencing variables. This fact is exploited to derive conditions for the lack of a moderating effect, the latter being a much discussed concept in the social science literature.