WASP (write a scientific paper): An introduction to set-theoretic methods and qualitative comparative analysis.

This paper provides an introduction to set-theoretic methods with respect to their application to research in the qualitative paradigm, as part of a series of papers on qualitative research being featured in Early Human Development. It discusses the philosophical assumptions underlying set-theoretic methods and the properties that make them well-suited for use in the analysis of qualitative data. It also takes a closer look at qualitative comparative analysis (QCA), a cross-case analysis method that has arguably been most widely applied among the set-theoretic methods and has also been gaining ground in the health field. Theoretical underpinnings, sample-size considerations, set calibration, QCA software packages, parameters of fit and limitations of the method are discussed. A description of the analytic output issued by a freely available software package, fs/QCA, is used as an example to illustrate QCA results and their interpretation.