Interest in the application of fuzzy set Qualitative Comparative Analysis (fsQCA) has increased markedly among political scientists in recent years. Although fsQCA is often contrasted with regression analysis, questions of functional form have thus far been hardly addressed. However, functional form matters as much in the former tool kit of social inquiry as it does in the latter. This article demonstrates how coverage as a measure of set-relational fit is influenced by the formulation of transformational rules similar to the coefficient of determination being influenced by functional specifications. Interaction effects between membership function and crossover anchor choice on coverage are analyzed in the context of set-theoretic relations of sufficiency between condition and outcome. Depending on the relative location of the crossover anchor, changes in the transformational rules by which metric base variables are calibrated can increase or decrease coverage. Most importantly, significant reductions in uncovered membership relative to total membership can be achieved because explicit foundations for calibration strategies are still lacking. While these results are independent of the number of observations, they carry additional significance for studies that combine fsQCA with the in-depth analysis of individual cases in mixed-method designs.
