In Sampling and Choosing Cases in Qualitative Research, Nick Emmel evaluates widely used sampling strategies, identifying key theoretical assumptions and considering how empirical and theoretical claims are made from these diverse methods. Drawing on case studies from across the social sciences Emmel shows how ideas drive choices, how cases are used to work out the relation between ideas and evidence, and why it is not the size of a sample that matters, it is how cases are used to interpret and explain that counts. Emily St Denny finds that the book’s greatest value lies in encouraging practitioners to reflect on the assumptions and choices we make regarding what we perceive to be the nature of existence, reality, and the purpose of social science research. 

Sampling and Choosing Cases in Qualitative Research: A Realist Approach. Nick Emmel. Sage. October 2013.

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Research is about making choices. As social scientists, the big choices concern what, why, and how we study. Once made, these choices tend to feature prominently and fixedly in our research. In Sampling and Choosing Cases in Qualitative Research: A Realist Approach, however, Nick Emmel problematises the notion that these choices are ever definitively made during the course of conducting research. Instead, argues Emmel, considering and selecting a topic to focus on is only meaningful as part of a sustained process of engagement with the observable empirical world, guided by the ideas we hold and develop about ‘reality’. The resulting nine-chapter book is both a compelling treatise calling for social scientists to engage more rigorously and explicitly with the key epistemological and ontological issues underpinning qualitative inquiry, and a clearly written and richly illustrated guide on how to go about conducting sound realist social science research.

The first, and shorter, part of the book defines, discusses, and contrasts the three different types of sampling strategies available to researchers in the social sciences: theoretical, purposeful, and theoretical or purposive. Briefly, theoretical sampling in grounded theory refers to the continual process by which cases are uncovered by researchers as they navigate the empirical world, while being guided by emergent theory. In this way, theoretical sampling remains ‘grounded’ in empirical data while allowing the theoretically open and sensitive researcher to be guided by interaction with, and structured comparison across, the observable world. It is contrasted to purposeful sampling, which aims to align pragmatism and functionality to identify and select the most appropriate, insightful, and convincing cases for developing and testing theoretical postulates in the context of applied research. Finally, theoretical or purposive sampling is presented as a highly interpretative and inductive strategy in which there is constant iteration between the phenomenon of interest and the explanation under development, which leads to the inclusion and exclusion of cases in accordance with the nature and scope of the claims the researcher wishes to make.

The second part of the book focuses on unpacking the practical and methodological implications of scientific realism in order to develop specifically realist sampling and casing strategies. Realists posit a real world, independent of our perceptions, theories, or constructions, which many social scientists assume, but which few of us ever probe or problematize. Thus, the realist sample is presented as both an empirical fact, and one that requires explanation and justification in order to derive its meaning. This part of the book therefore covers the mechanisms through which samples are generated, the employment of purposive casing, and the challenges arising from describing, analyzing, and interpreting ‘reality’ captured by samples and cases. Indeed, more so than the edifying technical guidance it offers, the book’s greatest added value lies in encouraging practitioners to reflect on the assumptions and choices we make regarding what we perceive to be the nature of existence, reality, and the purpose of social science research.

Throughout, all of the practical, methodological, and analytical issues raised are masterfully illustrated with extensive resort to rich and varied examples from the social science literature. For example, using Angela Browne’s psychological study of domestically abused women who go on to commit the murder of their intimate partner, Emmel demonstrates how several purposeful sampling strategies are often combined in light of a researcher’s theoretical and analytic objectives. Indeed, in order to shed light on some of the psychological processes that can lead to acts of extreme violence, Browne selected a sample that displayed homogeneity on certain dimensions – in order to establish recurring patterns and drawn contingent generalisations – and maximum variation on other dimensions, with the inclusion of extreme or deviant cases that reflect the fact that not all abused women go on to murder their partner.

Emmel also demonstrates how the purposive selection of an identical case can be motivated by different theoretical aspirations, using the example of the multiple studies of the city of Muncie, Indiana, over time. Indeed, the first study of Muncie, by Lynd and Lynd (1929), was motivated by the desire to capture the quintessence of social relations in middle America by using an archetypal American city as a ‘typical’ case. Later investigations of the same city, such as that by Goodall et al. (2004), instead aimed to shed light on some of the more insidious dynamics of racial and gender inequalities that pervade American society. This sustained engagement with the wealth of case study research across time and disciplines is, in itself, an example of best practice in research, and serves as an effective homage to the ongoing and cumulative nature of the social science project.

In addition to detailed discussion of notable case studies in social science research, Emmel also makes myriad brief and heuristic allusions to other works, which impel the curious reader to seek out and engage with the full works in their own time. This approach meshes well with Emmel’s predilection for using the parochial, usually in the form of folk tales, to illustrate facets of realist research and evinces a desire to put even the commonest of sense at the service of enlightenment. Thus, in order to illustrate the extent to which researchers’ previously held ideas and motivations can shape the way in which we sample cases and draw conclusions, Emmel uses the tale of Dr. John Snow and Edmund Cooper, who each identified putative causes of a cholera outbreak in 1850s London despite departing from different assumptions regarding contagion and propagation of disease. On the one hand, Snow believed that cholera was spread by drinking water and went on to identify the supposedly culpable water pump, on Broad Street, by mapping out and triangulating the houses of the most recent cases. On the other hand, Cooper, an engineer for the Metropolitan Commission of Sewers eager not to see the water system blamed, was driven by the belief that cholera was spread by decaying organic matter, and managed to prove the sewers were not to blame for the outbreak and deaths. Ultimately, Cooper’s ‘miasmic’ theory won out over Snow’s account and it would be decades before it was dethroned in public health theory.

Overall, far from the standard case study primer hinted at by the rather synoptic title, this book presents an overview of sampling and casing strategies for qualitative social science inquiry alongside systematic consideration of the foundational ontological and epistemological issues driving decision-making when conducting research. The book is most suited to practitioners and postgraduate students seeking to develop their understanding or manipulation of the principles and procedures that underlie rigorous qualitative case-based inquiry aimed at generating theoretical insights.

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Emily St.Denny is a 2^nd year PhD student at the University of Stirling, in Scotland. Her thesis investigates the role of ideas in shaping the trajectory of contemporary French prostitution policies. Her research allows her to combine her interest in public policy theory, contemporary French politics and women’s rights. Emily also has research interests and experience in theoretical approaches to public policy and political economy, ideational approaches to political science, and comparative qualitative methods in political science. She holds an MSc in Global Crime, Justice and Security from the University of Edinburgh and a BaHons in Journalism and Politics from the University of Stirling. Read more reviews by Emily.