# QCA: A Package for Qualitative Comparative Analysis

## Description

The package QCA contains functions to perform Qualitative Comparative Analysis, complemented with a graphical user interface. It implements the comparative method as first described by Ragin (1987), and extended by Cronqvist and Berg-Schlosser (2009) and Ragin (2000, 2008). QCA is a bridge between the qualitative and quantitative research methodologies, making use of the qualitative procedures in a systematic, algorithmic way (therefore increasing the “confidence” in the results, as understood by quantitative researchers).

The Quine-McCluskey minimization algorithms implemented in this package are mathematically exact, as described by Dusa (2007b), Dusa (2010), Dusa and Thiem (2015) and Dusa (2017). They all return the same, relevant set of prime implicants for csQCA (binary crisp sets QCA), mvQCA (multi-value QCA) and fsQCA (fuzzy-sets QCA).

Between versions 1.0-0 and up to version 1.1-3, the package welcomed a second co-author Alrik Thiem, responsible with the manual testing and documentation of functions, while the main author Adrian Dusa developed this software.

The package gained new functionality by employing and also other types of QCA like tsQCA (temporal QCA), see Caren and Panofsky (2005), Ragin and Strand (2008), and more recently also causal chains similar to those from the package cna (see Ambuehl et all 2015).

The results of the QCA package are consistent with (and sometimes even better than) the results of the other software packages for QCA, most notably fs/QCA by Ragin and Davey (2014) and Tosmana by Cronqvist and Berg-Schlosser (2009). A comparison of several such software is provided by Thiem and Dusa (2013).

From version 2.0, this package uses a new graphical user interface based on the package shiny. To avoid developing different interfaces for different operating systems, the current GUI was designed to work in a webpage. It uses a combination of HTML, CSS, jQuery for the user interface, a custom development framework using vector graphics based on the Raphael library, and extensive Javascript code to bind these altogether. A first version of this user interface was presented by Dusa (2007a), but users should be aware the current version is much more advanced. Starting with version 2.5, the user interface gained a web-based command console to offer a complete experience of available functionality.

Version 3.0 brings major improvements and additions, most notably the implementation of a new minimization algorithm called CCubes (Consistency Cubes), that is hundreds of times faster than the previous eQMC. Starting with version 3.5, it is possible to specify conjunctural directional expectations in the minimization function, and from version 3.14 categorical data is also recognized.

## Details

Package: | QCA
Version: | 3.20
Date: | 2023-07-11
License: | GPL (>= 3)

## References

Ambuehl, M. et all (2015) A Package for Coincidence Analysis (CNA), R Package Version 1.0-3 [Computer Program] URL: https://cran.r-project.org/package=cna.

Caren, N.; Panofsky, A. (2005) “TQCA: A Technique for Adding Temporality to Qualitative Comparative Analysis.” Sociological Methods & Research vol.34, no.2, pp.147-172.

Cronqvist, L. (2011) Tosmana: Tool for Small-N Analysis, Version 1.3.2.0 [Computer Program]. Trier: University of Trier.

Dusa, A. (2007a) “User manual for the QCA(GUI) package in R”. Journal of Business Research vol.60, no.5, pp.576-586.

Dusa, A. (2007b) Enhancing Quine-McCluskey. WP 2007-49, COMPASSS. URL: http://www.compasss.org/wpseries/Dusa2007b.pdf.

Dusa, A. (2010) “A Mathematical Approach to the Boolean Minimization Problem.” Quality & Quantity vol.44, no.1, pp.99-113.

Dusa, A. (2017) “Consistency Cubes: A Fast, Efficient Method for Boolean Minimization.” unpublished working paper on ResearchGate, DOI: RG.2.2.36359.19361/4

Dusa, A.; Thiem, A. (2015) “Enhancing the Minimization of Boolean and Multivalue Output Functions With eQMC” Journal of Mathematical Sociology vol.39, no.2, pp.92-108.

Ragin, C.C. (1987) The Comparative Method: Moving beyond Qualitative and Quantitative Strategies. Berkeley: University of California Press.

Ragin, C.C. (2000) Fuzzy-Set Social Science. Chicago: University of Chicago Press.

Ragin, C.C. (2008) Redesigning Social Inquiry: Fuzzy Sets and Beyond. Chicago: University of Chicago Press.

Ragin, C.C.; Strand, S.I. (2008) “Using Qualitative Comparative Analysis to Study Causal Order: Comment on Caren and Panofsky (2005)”. Sociological Methods & Research vol.36, no.4, pp.431-441.

Ragin, C.C.; Davey, S. (2014) fs/QCA: Fuzzy-Set/Qualitative Comparative Analysis, Version 2.5 [Computer Program]. Irvine: Department of Sociology, University of California.

Thiem, A.; Dusa, A. (2013) “Boolean Minimization in Social Science Research: A Review of Current Software for Qualitative Comparative Analysis (QCA).” Social Science Computer Review vol.31, no.4, pp.505-521.

## Author

Adrian Dușa
Department of Sociology
University of Bucharest
dusa.adrian@unibuc.ro
Maintainer:
Adrian Dușa