What is Necessity

This article concerns itself with qualitative comparative analysis (QCA), introduced in Ragin (1987), it is a technique that attempts to identify the causal relationship between variables and some outcome. QCA is employed in comparative case-oriented research, for studying a small-to-moderate number of cases in which a specific outcome has occurred, compared with those where it has not. Unlike conventional statistical analysis, however, QCA does not ask about the independent effect of a variable on the likelihood of an outcome. Rather, it considers configurations of values on the independent variables as cases (Ragin, 1987; Kitchener, Beynon, & Harrington, 2002). The central goal of QCA is to mimic some of the basic analytic procedures that comparative researchers use routinely when making sense of their cases. The key difference between QCA and traditional case-oriented methods is that with QCA it is possible to extend these basic analytic procedures to the examination of more than a handful of cases (Ragin & Rihoux, 2004).