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Fuzzy Sets on Shaky Ground: Parameter Sensitivity and Confirmation Bias in fsQCA

  • Chris Krogslund (a1), Donghyun Danny Choi (a2) and Mathias Poertner (a3)


Scholars have increasingly turned to fuzzy set Qualitative Comparative Analysis (fsQCA) to conduct small- and medium-N studies, arguing that it combines the most desired elements of variable-oriented and case-oriented research. This article demonstrates, however, that fsQCA is an extraordinarily sensitive method whose results are worryingly susceptible to minor parametric and model specification changes. We make two specific claims. First, the causal conditions identified by fsQCA as being sufficient for an outcome to occur are highly contingent upon the values of several key parameters selected by the user. Second, fsQCA results are subject to marked confirmation bias. Given its tendency toward finding complex connections between variables, the method is highly likely to identify as sufficient for an outcome causal combinations containing even randomly generated variables. To support these arguments, we replicate three articles utilizing fsQCA and conduct sensitivity analyses and Monte Carlo simulations to assess the impact of small changes in parameter values and the method's built-in confirmation bias on the overall conclusions about sufficient conditions.


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Authors' note: Supplementary materials for this article are available on the Political Analysis Web site. (Chris Krogslund, Donghyun Danny Choi, and Mathias Poertner, 2014, “Fuzzy Sets on Shaky Ground: Parameter Sensitivity and Confirmation Bias in fsQCA”, Dataverse [Distributor] V1 [Version]). We thank the editors, the anonymous reviewers, Henry Brady, Ruth Berins Collier, Thad Dunning, Zachary Elkins, Marcus Kurtz, Katherine Michel, Robert Mickey, Gerardo Munck, Jack Paine, Slim Pickens, Roxanna Ramzipoor, Ingo Rohlfing, Jason Seawright, Laura Stoker, Sean Tanner, Alrik Thiem, Alison Varney, and Sherry Zaks for their very helpful comments. A special note of thanks goes out to David Collier, who was instrumental in shaping this project.



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Fuzzy Sets on Shaky Ground: Parameter Sensitivity and Confirmation Bias in fsQCA

  • Chris Krogslund (a1), Donghyun Danny Choi (a2) and Mathias Poertner (a3)


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