Qualitative Comparative Analysis (QCA) and Fuzzy Sets. 24 June 2013: Code of Good Standards. Prof. Dr. Claudius Wagemann

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1 Institut für Politikwissenschaft Schwerpunkt qualitative empirische Sozialforschung Goethe-Universität Frankfurt Fachbereich 03 Prof. Dr. Claudius Wagemann Qualitative Comparative Analysis (QCA) and 24 June 2013: Code of Good Standards

2 The Appropriateness of Set-Theoretic Methods Summarizing data (e.g., through a truth table, but also through a solution formula) Evaluation of existing hypotheses and theories Development of new arguments (Creation of typologies) 2

3 The Choice of the Conditions and the Outcome Dysfunctionality of having too many conditions Reduction of the number of conditions through the creation of higher-order constructs Ongoing refinement and reduction of the number of conditions is an integral part of QCA 3

4 The Choice of the QCA Variant Depends on the type of concepts Depends on the empirical data at hand Fuzzy sets are preferable, since they contain more information than crisp sets and set higher standards for subset relations. Does not depend on the number of cases 4

5 Calibration of Set Membership Scores Detailed documentation Conventional forms of index building or direct/indirect method of calibration Determination of qualitative anchors (0, 0.5 and 1) through theoretical knowledge external to the data Explicit arguments on differences in degree 5

6 Analysis of Necessary Conditions Necessity must not be inferred from the analysis of a sufficiency analysis. Consistency values for necessity should not be lower than 0.9. The analysis of necessity preceeds the analysis of sufficiency. The use of functional equivalents has to be justified on theoretical grounds. 6

7 Analysis of Sufficient Conditions: Threshold Levels for Raw Consistency Logical contradictions have to be resolved prior to minimization. Minimum threshold for raw consistency has to be reported. Appropriate level specific to every individual research project. Rule of thumb: well above

8 Analysis of Sufficient Conditions: Treatment of Logical Remainders Treatment of logical remainders should be transparent. Possibility to express limited diversity in a Boolean expression. Incoherent or implausible assumptions have to be avoided. Not too many directional expectations have to be made. The enhanced intermediate solution should be at the center of the substantive discussion. 8

9 Analysis of Sufficient Conditions: Analysis of the Negative Outcome Separate analyses for the outcome and its negation. DeMorgan s Law can hardly ever be applied directly. Contradictory simplifying assumptions have to be avoided. Often: even a different truth table/different set of conditions is needed. 9

10 Presentation of Results Graphical forms: Venn diagrams XY plots Tabular forms: Truth tables Tables displaying each case s membership in all sufficient paths, the overall solution term and the outcome. Solution term with all parameters of fit Information on true logical contradictions Information on the uncovered cases with Y >

11 Interpretation of Results Focus on individual (groups of) cases Focus on parts of the solution Inconsistent paths should not be interpreted at all. Theoretical importance of paths often deviates from empirical importance, measured in terms of coverage. Focusing on single components of a conjunction usually runs counter the spirit of QCA. 11

12 Use of Software fsqca Does not do mvqca Does not list which cases are in which truth table row Does not list the simplifying assumptions Is not syntax-based 12

13 Use of Software TOSMANA Does not have a codable truth table Does not give an intermediate solution term Does not give the parameters of fit Does not do fsqca Does not do the analysis of necessity Does not produce XY plots Does not calculate PRI and PRODUCT measures Is not syntax-based 13

14 Use of Software STATA Does not have a codable truth table Does not give an intermediate solution term Does not do mvqca Does not list which cases are in which truth table row Does not list the simplifying assumptions Does not calculate PRI and PRODUCT measures 14

15 Use of Software R (package QCA, QCAGUI, QCA3) Does not have a codable truth table Does not give an intermediate solution term Does not calculate PRI and PRODUCT measures 15

16 Use of Software Software packages are quickly evolving. No single package alone is capable of performing all tasks needed for a good QCA. R is promising, but is not very recognized, not even in the statistical camp 16