Case Selection via Matching

Abstract

This article shows how statistical matching methods can be used to select “most similar” cases for qualitative analysis. I first offer a methodological justification for research designs based on selecting most similar cases. I then discuss the applicability of existing matching methods to the task of selecting most similar cases and propose adaptations to meet the unique requirements of qualitative analysis. Through several applications, I show that matching methods have advantages over traditional selection in “most similar” case designs: They ensure that most similar cases are in fact most similar; they make scope conditions, assumptions, and measurement explicit; and they make case selection transparent and replicable.

Quotas and Party Priorities: Direct and Indirect Effects of Quota Laws

“…While I would ideally like to match on other underlying party-and country-characteristics, a larger number of covariates will increase the distance between units in the covariate space, meaning matched pairs will be generally further apart (Nielsen & Sheffield 2012). However, I do adjust for other variables in the post-matching regression analysis, namely: female labor force participation and GDP per capita (both linked to attitudes towards women, like the matching variable women in the party).…”

case selection and the comparative method: introducing the case selector

“…The necessary and sufficient conditions approach to comparative designs expects that cases will align appropriately on each specific dimension. Nielsen (2016) is similarly critical of the propensity scores approach, pointing out that many suggestions for matching encourage case study researchers to adopt a 'statistical world view.' Nielsen further echoes our concerns that many proposals for matching were developed by statisticians to facilitate large-N analysis and were not designed to extract a small number of cases that would be best suited for further exploration in comparative case designs.…”

“…The Case Selector follows the practices of earlier computational case selection programs (Nielsen, 2016;Yang et al, 2003). Differences between cases are measured using Mahalanobis distances.…”

“…This is not to say that progress has not been made. Work by Nielsen (2016) has paved the way forward in the development of algorithmic approaches for case selection. While Gerring and Cojocaru (2016) are of mixed mind about the value of algorithmic case selection, they recognize movement in this direction.…”

A method for case selection in strategic urban planning

“…The method of case selection which will be used in the research is crucial for a qualitative research, such as urban studies (Nielsen, 2016). In practice, the case selection is often made without a detailed analysis of the processes and the context in which the case is located (Seawright & Gerring, 2008).…”