Paradoxes and pitfalls in using fuzzy set QCA: illustrations from a critical review of a study of educational inequality

Abstract

Charles Ragin's crisp set and fuzzy set Qualitative Comparative Analysis (csQCA and fsQCA) are being used by increasing numbers of social scientists interested in combining analytic rigour with case-based approaches. As with all techniques that become available in easy-to-use software packages, there is a danger that QCA will come to be used in a routinised manner, with not enough attention being paid to its particular strengths and weaknesses. Users of fsQCA in particular need to be very aware of particular problems that can arise when fuzzy logic lies behind their analyses. This paper aims to increase its readers' understanding of some of these problems and of some means by which they might be alleviated. We use a critical discussion of a recent paper by Freitag and Schlicht addressing social inequality in education in Germany as our vehicle. After summarising the substantive claims of the paper, we explain some key features of QCA. We subsequently discuss two main issues, (i) limited diversity and the various ways of using counterfactual reasoning to address it, and (ii) the logical paradoxes that can arise when using fsQCA. Making different choices than Freitag and Schlicht do in respect of dealing with these two issues, we undertake some reanalysis of their data, showing that their conclusions must be treated with some caution. We end by drawing some general lessons for users of QCA.