# 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 algorithm implemented in this package is mathematically exact, as described by Dusa (2007), Dusa (2010) and Dusa and Thiem (2015). It returns the relevant prime implicants for both csQCA (binary crisp sets QCA) and also for mvQCA (multi-value QCA, as of version 0.6-0).

Starting with version 0.4-5 the package QCA gained a new function called `eqmcc` (from "e"nhanced Quine-McCluskey) that finds exact solutions with a substantially lower memory consumption.

Since version 1.0-0, the package QCA welcomed a second co-author Alrik Thiem (up to version 1.1-3), responsible with the manual testing and documentation of functions, while Adrian Dusa was responsible with all of the software development. The package gained new functionality by employing fsQCA (fuzzy-set QCA) and also other types of QCA like tsQCA (temporal QCA), see Caren and Panofsky (2005), Ragin and Strand (2008). The package is also able to obtain the causal chains similar to those from the package cna (see Ambuehl et all 2015).

The results of the QCA package are very 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. In order to avoid developing different interfaces for different operating systems, the current GUI was designed to work into 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 (2007), but users should be aware the current version is much more advanced.

The author of this package is grateful for the effort of the former coauthor of the QCA package, Alrik Thiem, given his responsibilities of testing and documenting the functions. Although the current documentation is completely re-written, it owes a great deal of impact from the previous versions.

## Details

Package:
QCA
Type:
Package
Version:
2.5
Date:
2016-05-05
License:
GPL (>= 2)

## 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.; 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

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