Editing Case study

{{Short description|In-depth, detailed examination of a particular case}}
A '''case study''' is an in-depth, detailed examination of a particular case (or cases) within a real-world context.<ref>{{cite book | last=Bromley | first=D. B. | title=The case-study method in psychology and related disciplines | publisher=Wiley | publication-place=Chichester | date=1986 | isbn=0-471-90853-3 | oclc=12235475}}</ref><ref>{{cite book | last1=Feagin | first1=Joe R. | last2=Orum | first2=Anthony M. | last3=Sjoberg | first3=Gideon | title=A Case for the case study | publisher=University of North Carolina Press | publication-place=Chapel Hill | date=1991 | isbn=0-8078-1973-5 | oclc=22909879}}</ref> For example, case studies in [[medicine]] may focus on an individual patient or ailment; case studies in [[business]] might cover a particular [[firm]]'s strategy or a broader [[Market (economics)|market]]; similarly, case studies in [[politics]] can range from a narrow happening over time like the operations of a specific [[political campaign]], to an enormous undertaking like [[world war]], or more often the [[policy analysis]] of real-world problems affecting multiple stakeholders.

Generally, a case study can highlight nearly any individual, group, organization, event, belief system, or action. A case study does not necessarily have to be one observation ([[Sample (statistics)|N]]=1), but may include many observations (one or multiple individuals and entities across multiple time periods, all within the same case study).<ref name=":11">{{Cite book|last=Geddes|first=Barbara|title=Paradigms and Sand Castles|date=2003|publisher=University of Michigan Press|isbn=978-0-472-09835-4|location=Ann Arbor, MI|pages=117|doi=10.3998/mpub.11910}}</ref><ref name=":12">{{Cite book|last1=King|first1=Gary|title=Designing Social Inquiry|last2=Keohane|first2=Robert O.|last3=Verba|first3=Sidney|date=1994|publisher=Princeton University Press|isbn=978-1-4008-2121-1|location=Princeton, New Jersey|pages=52–53|doi=10.1515/9781400821211}}</ref><ref name=":13">{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=1, 19–20|language=en}}</ref><ref name=":14">{{Cite journal|last=Thies|first=Cameron G.|date=2002|title=A Pragmatic Guide to Qualitative Historical Analysis in the Study of International Relations|url=https://www.jstor.org/stable/44218229|journal=International Studies Perspectives|volume=3|issue=4|pages=351–372|doi=10.1111/1528-3577.t01-1-00099|jstor=44218229|issn=1528-3577|url-access=subscription}}</ref> Research projects involving numerous cases are frequently called cross-case research, whereas a study of a single case is called within-case research.<ref name=":13" /><ref name=":15">{{Cite book|last1=George|first1=Alexander L.|url=https://books.google.com/books?id=JEGzE6ExN-gC|title=Case Studies and Theory Development in the Social Sciences|last2=Bennett|first2=Andrew|date=2005|publisher=MIT Press|isbn=978-0-262-57222-4|pages=18|language=en}}</ref>

Case study research has been extensively practiced in both the [[Social science|social]] and [[natural science]]s.<ref name="Mills2010">{{cite book |editor1-last=Mills |editor1-first=Albert J. |editor2-first=Gabrielle |editor2-last=Durepos |editor3-first=Elden |editor3-last=Wiebe |title=Encyclopedia of Case Study Research |publisher=SAGE Publications |location=Thousand Oaks, CA |year=2010 |page=xxxi |isbn=978-1-4129-5670-3 }}</ref><ref name="Yin">{{cite book |last=Yin |first=Robert K. |author-link=Robert K. Yin |title=Case Study Research: Design and Methods |url={{GBurl|OgyqBAAAQBAJ}} |edition=6th |year=2017 |publisher=SAGE Publications |location=Thousand Oaks, California, US |isbn=978-1-5063-3616-9}}</ref>{{rp|5–6}}<ref name="Rolls2005">{{cite book|title=Classic Case Studies in Psychology|last=Rolls|first=Geoffrey|publisher=Hodder Education|year=2005|location=Abingdon, England}}</ref><ref>{{Cite book |first1=Marilyn L. |last1=Taylor |first2=Mikael |last2=Søndergaard |title=Unraveling the Mysteries of Case Study Research: A Guide for Business and Management Students|publisher=Edward Elgar Publishing|year=2017|isbn=978-1786437235}}</ref>

== Definition ==
There are multiple definitions of case studies, which may emphasize the number of [[observation]]s (a small N), the method ([[Qualitative research|qualitative]]), the thickness of the research (a comprehensive examination of a phenomenon and its context), and the naturalism (a "real-life context" is being examined) involved in the research.<ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=17|language=en}}</ref> There is general agreement among scholars that a case study does not necessarily have to entail one observation (N=1), but can include many observations within a single case or across numerous cases.<ref name=":11" /><ref name=":12" /><ref name=":13" /><ref name=":14" /> For example, a case study of the [[French Revolution]] would at the bare minimum be an observation of two observations: France before and after a revolution.<ref name=":16">{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=29–32|language=en}}</ref> John Gerring writes that the N=1 research design is so rare in practice that it amounts to a "myth".<ref name=":16" />

The term ''cross-case'' research is frequently used for studies of multiple cases, whereas ''within-case'' research is frequently used for a single case study.<ref name=":13" /><ref name=":15" />

John Gerring defines the case study approach as an "intensive study of a single unit or a small number of units (the cases), for the purpose of understanding a larger class of similar units (a population of cases)".<ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=37|language=en}}</ref> According to Gerring, case studies lend themselves to an [[Nomothetic and idiographic|idiographic]] style of analysis, whereas [[Quantitative research|quantitative]] work lends itself to a [[Nomothetic and idiographic|nomothetic]] style of analysis.<ref name=":20">{{Cite journal|last=Gerring|first=John|date=2017|title=Qualitative Methods|journal=Annual Review of Political Science|language=en|volume=20|issue=1|pages=15–36|doi=10.1146/annurev-polisci-092415-024158|issn=1094-2939|doi-access=free}}</ref> He adds that "the defining feature of qualitative work is its use of noncomparable observations—observations that pertain to different aspects of a causal or descriptive question", whereas quantitative observations are comparable.<ref name=":20" />

According to John Gerring, the key characteristic that distinguishes case studies from all other methods is the "reliance on evidence drawn from a single case and its attempts, at the same time, to illuminate features of a broader set of cases".<ref name=":16" /> Scholars use case studies to shed light on a "class" of phenomena.

== Research design ==

As with other social science methods, no single research design dominates case study research. Case studies can use at least four types of designs. First, there may be a "no theory first" type of case [[study design]], which is closely connected to [[Kathleen M. Eisenhardt]]'s methodological work.<ref name="Ridder2017">{{cite journal|last=Ridder|first=Hans-Gerd|date=October 2017|title=The theory contribution of case study research designs|journal=Business Research|volume=10|issue=2|pages=281–305|doi=10.1007/s40685-017-0045-z|issn=2198-2627|doi-access=free|hdl=10419/177270|hdl-access=free}}</ref><ref name="Eisenhardt1991">{{cite journal |last=Eisenhardt |first=Kathleen M. |author-link=Kathleen M. Eisenhardt |title=Better Stories and Better Constructs: The Case for Rigor and Comparative Logic |journal=The Academy of Management Review |volume=16 |issue=3 |pages=620–627 |year=1991 |jstor=258921 |doi=10.5465/amr.1991.4279496 }}</ref> A second type of research design highlights the distinction between single- and multiple-case studies, following [[Robert K. Yin]]'s guidelines and extensive examples.<ref name="Ridder2017" /><ref name="Yin" /> A third design deals with a "social construction of reality", represented by the work of [[Robert E. Stake]].<ref name="Ridder2017" /><ref name="Stake1995">{{cite book |last=Stake |first=Robert E. |author-link=Robert E. Stake |title=The Art of Case Study Research |url={{GBurl|ApGdBx76b9kC|pg=PR99}} |pages=99–102 |year=1995 |publisher=SAGE Publications |location=Thousand Oaks, CA |isbn=978-0-8039-5767-1}}</ref> Finally, the design rationale for a case study may be to identify "anomalies". A representative scholar of this design is [[Michael Burawoy]].<ref name="Ridder2017" /><ref name="Burawoy2009">{{cite book |last=Burawoy |first=Michael |author-link=Michael Burawoy |title=The Extended Case Method: Four Countries, Four Decades, Four Great Transformations, and One Theoretical Tradition |url={{GBurl|xCA7R-o8BMIC}} |year=2009 |publisher=University of California Press |location=Berkeley |isbn=978-0-520-94338-4 }}</ref> Each of these four designs may lead to different applications, and understanding their sometimes unique [[ontology|ontological]] and [[epistemology|epistemological]] assumptions becomes important. However, although the designs can have substantial methodological differences, the designs also can be used in explicitly acknowledged combinations with each other.

While case studies can be intended to provide bounded explanations of single cases or phenomena, they are often intended to raise theoretical insights about the features of a broader population.<ref name=":2" />

=== Case selection and structure ===

Case selection in case study research is generally intended to find cases that are representative samples and which have variations on the dimensions of theoretical interest.<ref name=":2" /> Using that is solely representative, such as an average or typical case is often not the richest in information. In clarifying lines of history and causation it is more useful to select subjects that offer an interesting, unusual, or particularly revealing set of circumstances. A case selection that is based on representativeness will seldom be able to produce these kinds of insights.

While a random selection of cases is a valid case selection strategy in [[Big data|large-N]] research, there is a consensus among scholars that it risks generating serious biases in small-N research.<ref name=":6" /><ref name=":3" /><ref name=":2" /><ref name=":18">{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=87|language=en|quote=Random sampling is unreliable in small-N research}}</ref> Random selection of cases may produce unrepresentative cases, as well as uninformative cases.<ref name=":18" /> Cases should generally be chosen that have a high expected information gain.<ref name=":7" /><ref name=":2" /><ref name=":9">{{Citation|last=Seawright|first=Jason|title=Case Selection after Regression|date=2016|url=https://www.cambridge.org/core/books/multimethod-social-science/case-selection-after-regression/5A581A473A1D9ADBFA98A5DE607B4DA4|work=Multi-Method Social Science: Combining Qualitative and Quantitative Tools|volume=|pages=75–106|publisher=Cambridge University Press|doi=10.1017/cbo9781316160831.004|isbn=978-1-107-09771-1|access-date=2021-02-11|url-access=subscription}}</ref> For example, [[outlier]] cases (those which are extreme, deviant or atypical) can reveal more information than the potentially representative case.<ref name=":9" /><ref name="Huang2015">{{cite book |last1=Huang |first1=Huayi |year=2015 |title=Development of New Methods to Support Systemic Incident Analysis |type=Doctoral dissertation |publisher=Queen Mary University |location=London |url=https://qmro.qmul.ac.uk/xmlui/bitstream/handle/123456789/12866/Huang_Huayi_PhD_Final_111115.pdf }}{{page needed|date=December 2017}}</ref><ref name="Underwood2016">{{cite journal |doi=10.1016/j.ssci.2015.08.014 |title='Accident investigation in the wild' – A small-scale, field-based evaluation of the STAMP method for accident analysis |journal=[[Safety Science]] |volume=82 |pages=129–43 |year=2016 |last1=Underwood |first1=Peter |last2=Waterson |first2=Patrick |last3=Braithwaite |first3=Graham }}</ref> A case may also be chosen because of the inherent interest of the case or the circumstances surrounding it. Alternatively, it may be chosen because of researchers' in-depth local knowledge; where researchers have this local knowledge they are in a position to "soak and poke" as [[Richard Fenno]] put it,<ref name=" Fenno2014">{{cite journal |last=Fenno |first=Richard F. |author-link=Richard Fenno |title=Observation, Context, and Sequence in the Study of Politics |journal=American Political Science Review |volume=80 |issue=1 |pages=3–15 |year=2014 |doi=10.2307/1957081 |jstor=1957081 |s2cid=145630377 }}</ref> and thereby to offer reasoned lines of explanation based on this rich knowledge of setting and circumstances.

Beyond decisions about case selection and the subject and object of the study, decisions need to be made about the purpose, approach, and process of the case study. [[Gary Thomas (academic)|Gary Thomas]] thus proposes a typology for the case study wherein purposes are first identified (evaluative or exploratory), then approaches are delineated (theory-testing, theory-building, or illustrative), then processes are decided upon, with a principal choice being between whether the study is to be single or multiple, and choices also about whether the study is to be retrospective, snapshot or diachronic, and whether it is nested, parallel or sequential.<ref name="Thomas">{{cite journal |doi=10.1177/1077800411409884 |title=A Typology for the Case Study in Social Science Following a Review of Definition, Discourse, and Structure |journal=Qualitative Inquiry |volume=17 |issue=6 |pages=511–21 |year=2011 |last=Thomas |first=Gary |s2cid=144895919 |author-link=Gary Thomas (academic) |url=https://zenodo.org/record/894078 }}</ref>

In a 2015 article, John Gerring and Jason Seawright list seven case selection strategies:<ref name=":2">{{Citation|last1=Seawright|first1=Jason|title=Case Selection Techniques in Case Study Research: A Menu of Qualitative and Quantitative Options|work=Political Research Quarterly|volume=|pages=|year=2014|doi=10.4135/9781473915480.n31|isbn=978-1-4462-7448-4|last2=Gerring|first2=John}}</ref>

# Typical cases are cases that exemplify a stable cross-case relationship. These cases are representative of the larger population of cases, and the purpose of the study is to look ''within'' the case rather than compare it with other cases.
# Diverse cases are cases that have variations on the relevant X and Y variables. Due to the range of variation on the relevant variables, these cases are representative of the full population of cases.
# Extreme cases are cases that have an extreme value on the X or Y variable relative to other cases.
# Deviant cases are cases that defy existing theories and common sense. They not only have extreme values on X or Y (like extreme cases) but defy existing knowledge about causal relations.
# Influential cases are cases that are central to a model or theory (for example, Nazi Germany in theories of fascism and the far-right).
# Most similar cases are cases that are similar on all the [[independent variables]], except the one of interest to the researcher.
# Most different cases are cases that are different on all the independent variables, except the one of interest to the researcher.
For theoretical discovery, Jason Seawright recommends using deviant cases or extreme cases that have an extreme value on the X variable.<ref name=":9" />

[[Arend Lijphart]], and [[Harry H. Eckstein|Harry Eckstein]] identified five types of case study research designs (depending on the research objectives), Alexander George and Andrew Bennett added a sixth category:<ref>{{Cite book|last1=George|first1=Alexander L.|title=Case Studies and Theory Development in the Social Sciences|last2=Bennett|first2=Andrew|date=2005|publisher=MIT Press|isbn=978-0-262-30307-1|pages=74–76, 213|oclc=944521872}}</ref>

# Atheoretical (or configurative idiographic) case studies aim to describe a case very well, but not to contribute to a theory.
# Interpretative (or disciplined configurative) case studies aim to use established theories to explain a specific case.
# Hypothesis-generating (or heuristic) case studies aim to inductively identify new variables, hypotheses, causal mechanisms, and causal paths.
# Theory testing case studies aim to assess the validity and scope conditions of existing theories.
# Plausibility probes, aim to assess the plausibility of new hypotheses and theories.
# Building block studies of types or subtypes, aim to identify common patterns across cases.

Aaron Rapport reformulated "least-likely" and "most-likely" case selection strategies into the "countervailing conditions" case selection strategy. The countervailing conditions case selection strategy has three components:<ref>{{Cite journal|last=Rapport|first=Aaron|date=2015|title=Hard Thinking about Hard and Easy Cases in Security Studies|url=http://www.tandfonline.com/doi/full/10.1080/09636412.2015.1070615|journal=Security Studies|language=en|volume=24|issue=3|pages=431–465|doi=10.1080/09636412.2015.1070615|s2cid=131769695|issn=0963-6412}}</ref>

# The chosen cases fall within the scope conditions of both the primary theory being tested and the competing alternative hypotheses.
# For the theories being tested, the analyst must derive clearly stated expected outcomes.
# In determining how difficult a test is, the analyst should identify the strength of countervailing conditions in the chosen cases.

In terms of case selection, [[Gary King (political scientist)|Gary King]], [[Robert Keohane]], and [[Sidney Verba]] warn against "selecting on the [[dependent variable]]". They argue for example that researchers cannot make valid causal inferences about war outbreaks by only looking at instances where war did happen (the researcher should also look at cases where war did not happen).<ref name=":3" /> Scholars of qualitative methods have disputed this claim, however. They argue that selecting the dependent variable can be useful depending on the purposes of the research.<ref name=":7" /><ref name=":8" /><ref name=":10" /> Barbara Geddes shares their concerns with selecting the dependent variable (she argues that it cannot be used for theory testing purposes), but she argues that selecting on the dependent variable can be useful for theory creation and theory modification.<ref name=":0" />

King, Keohane, and Verba argue that there is no methodological problem in selecting the [[explanatory variable]], however. They do warn about [[multicollinearity]] (choosing two or more explanatory variables that perfectly correlate with each other).<ref name=":3">King, Gary/ Keohane, Robert O./ Verba, Sidney: ''Designing Social Inquiry. Scientific Inference in Qualitative Research''. Princeton University Press, 1994.</ref>

==Uses==
Case studies have commonly been seen as a fruitful way to come up with hypotheses and generate theories.<ref name=":6">{{Citation|last=Levy|first=Jack|title=Case Studies: Types, Designs, and Logics of Inference|work=Case Studies|year=2014|pages=II113|publisher=SAGE Publications Ltd|doi=10.4135/9781473915480.n26|isbn=978-1-4462-7448-4}}</ref><ref name=":3" /><ref name=":7">{{Cite book|last1=George|first1=Alexander L.|title=Case Studies and Theory Development in the Social Sciences|last2=Bennett|first2=Andrew|date=2005|publisher=MIT Press|isbn=978-0-262-30307-1|location=|oclc=944521872}}</ref><ref name=":17">{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=39–40|language=en}}</ref><ref name=":20" /> Case studies are useful for understanding outliers or deviant cases.<ref name=":21">{{Citation |last1=Widner |first1=Jennifer |title=Using Case Studies to Enhance the Quality of Explanation and Implementation: Integrating Scholarship and Development Practice |date=2022 |url=https://www.cambridge.org/core/books/case-for-case-studies/using-case-studies-to-enhance-the-quality-of-explanation-and-implementation/FACFB9C877AAAD65909220E80E3074C7 |work=The Case for Case Studies: Methods and Applications in International Development |pages=1–26 |editor-last=Ortega Nieto |editor-first=Daniel |publisher=Cambridge University Press |isbn=978-1-108-42727-2 |last2=Woolcock |first2=Michael |last3=Nieto |first3=Daniel Ortega |editor2-last=Widner |editor2-first=Jennifer |editor3-last=Woolcock |editor3-first=Michael}}</ref> Classic examples of case studies that generated theories includes Darwin's [[theory of evolution]] (derived from his travels to the Galapagos Islands), and [[Douglass North]]'s theories of economic development (derived from case studies of early developing states, such as England).<ref name=":17" />

Case studies are also useful for formulating [[concept]]s, which are an important aspect of theory construction.<ref name=":02">{{Cite journal|last=Mahoney|first=James|date=2010|title=After KKV: The New Methodology of Qualitative Research|url=https://www.cambridge.org/core/journals/world-politics/article/after-kkv-the-new-methodology-of-qualitative-research/4A72E003336B3D44D47B053513B43F53|journal=World Politics|language=en|volume=62|issue=1|pages=120–147|doi=10.1017/S0043887109990220|s2cid=43923978|issn=1086-3338|url-access=subscription}}</ref> The concepts used in qualitative research will tend to have higher conceptual validity than concepts used in quantitative research (due to [[Giovanni Sartori|conceptual stretching]]: the unintentional comparison of dissimilar cases).<ref name=":7" /> Case studies add descriptive richness,<ref name=":5">{{Cite journal|last=Collier|first=David|date=2011|title=Understanding Process Tracing|journal=PS: Political Science & Politics|volume=44|issue=4|pages=823–830|doi=10.1017/s1049096511001429|issn=1049-0965|doi-access=free}}</ref><ref name=":10">{{Cite book|last1=Brady |first1=Henry E. |last2=Collier |first2=David|title=Rethinking social inquiry : diverse tools, shared standards|date=2010|publisher=Rowman & Littlefield Publishers|isbn=978-1-4422-0343-3|edition=2|location=|pages=|oclc=838295613}}</ref> and can have greater internal validity than quantitative studies.<ref name=":19">{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=43, 49|language=en}}</ref> Case studies are suited to explain outcomes in individual cases, which is something that quantitative methods are less equipped to do.<ref name=":8">{{Cite book|last1=Goertz|first1=Gary|url=http://dx.doi.org/10.23943/princeton/9780691149707.001.0001|title=A Tale of Two Cultures|last2=Mahoney|first2=James|date=2012-09-09|publisher=Princeton University Press|isbn=978-0-691-14970-7|location=|pages=221–227|doi=10.23943/princeton/9780691149707.001.0001}}</ref> Case studies have been characterized as useful to assess the plausibility of arguments that explain empirical regularities.<ref>{{Cite web|last1=Fearon|first1=James D.|last2=Laitin|first2=David D.|editor1-first=Robert E|editor1-last=Goodin|date=2011|title=Integrating Qualitative and Quantitative Methods|url=https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199604456.001.0001/oxfordhb-9780199604456-e-052|url-status=live|website=The Oxford Handbook of Political Science|language=en|doi=10.1093/oxfordhb/9780199604456.001.0001|isbn=978-0-19-960445-6|archive-url=https://web.archive.org/web/20140530035109/http://www.oxfordhandbooks.com:80/view/10.1093/oxfordhb/9780199604456.001.0001/oxfordhb-9780199604456-e-052 |archive-date=2014-05-30 }}</ref> By emphasizing context across cases, case studies can be useful in identifying scope conditions and evaluating to what extent concepts and theories apply across cases.<ref>{{Cite journal |last=Simmons |first=Erica S. |last2=Smith |first2=Nicholas Rush |date=2025 |title=How Cases Speak to One Another: Using Translation to Rethink Generalization in Political Science Research |url=https://www.cambridge.org/core/journals/american-political-science-review/article/how-cases-speak-to-one-another-using-translation-to-rethink-generalization-in-political-science-research/CC25A63B221A1644C892128BEDECBAFA#article |journal=American Political Science Review |language=en |doi=10.1017/S0003055425000140 |issn=0003-0554|url-access=subscription }}</ref>

Through fine-grained knowledge and description, case studies can fully specify the causal mechanisms in a way that may be harder in a large-N study.<ref>{{Cite journal|last1=Bennett|first1=Andrew|last2=Elman|first2=Colin|date=2006|title=Qualitative Research: Recent Developments in Case Study Methods|journal=Annual Review of Political Science|language=en|volume=9|issue=1|pages=455–476|doi=10.1146/annurev.polisci.8.082103.104918|issn=1094-2939|doi-access=free}}</ref><ref name=":5" /><ref>Braumoeller, Bear and Anne Sartori. 2004. "The Promise and Perils of Statistics in International Relations." in ''Cases, Numbers, Models: International Relations Research Methods''. Ann Arbor: University of Michigan Press: ch. 6.</ref><ref name=":6" /><ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=42|language=en}}</ref><ref name=":21" /> In terms of identifying "causal mechanisms", some scholars distinguish between "weak" and "strong chains". Strong chains actively connect elements of the causal chain to produce an outcome whereas weak chains are just intervening variables.<ref>{{Cite journal|last=Waldner|first=David|date=2015-06-22|title=Process Tracing and Qualitative Causal Inference|url=https://www.tandfonline.com/doi/full/10.1080/09636412.2015.1036624|journal=Security Studies|volume=24|issue=2|pages=239–250|language=en|doi=10.1080/09636412.2015.1036624|s2cid=143163960|issn=0963-6412|url-access=subscription}}</ref>

Case studies of cases that defy existing theoretical expectations may contribute knowledge by delineating why the cases violate theoretical predictions and specifying the scope conditions of the theory.<ref name=":6" /> Case studies are useful in situations of causal complexity where there may be [[equifinality]], complex [[Interaction (statistics)|interaction effects]] and [[Path dependence|path dependency]].<ref name=":7" /><ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=61–62|language=en}}</ref> They may also be more appropriate for empirical verifications of [[strategic interaction]]s in rationalist scholarship than quantitative methods.<ref>{{Cite journal|last1=Farrell|first1=Henry|last2=Finnemore|first2=Martha|date=2009|title=Ontology, methodology, and causation in the American school of international political economy|url=https://doi.org/10.1080/09692290802524075|journal=Review of International Political Economy|volume=16|issue=1|pages=58–71|doi=10.1080/09692290802524075|issn=0969-2290|s2cid=145230528}}</ref> Case studies can identify necessary and insufficient conditions, as well as complex combinations of necessary and sufficient conditions.<ref name=":7" /><ref name=":8" /><ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=54–55|language=en}}</ref> They argue that case studies may also be useful in identifying the scope conditions of a theory: whether variables are sufficient or necessary to bring about an outcome.<ref name=":7" /><ref name=":8" />

Qualitative research may be necessary to determine whether a treatment is as-if random or not. As a consequence, good quantitative [[Observational techniques|observational research]] often entails a qualitative component.<ref name=":20" />

==Limitations==
''[[Designing Social Inquiry]]'' (also called "KKV"), an influential 1994 book written by [[Gary King (political scientist)|Gary King]], [[Robert Keohane]], and [[Sidney Verba]], primarily applies lessons from regression-oriented analysis to qualitative research, arguing that the same logics of causal inference can be used in both types of research.<ref name=":3" /><ref name=":1">{{Cite journal|last1=Humphreys|first1=Macartan|last2=Jacobs|first2=Alan M.|date=2015|title=Mixing Methods: A Bayesian Approach|journal=American Political Science Review|volume=109|issue=4|pages=654|doi=10.1017/s0003055415000453|s2cid=1846974|issn=0003-0554}}</ref><ref name=":02"/> The authors' recommendation is to increase the number of observations (a recommendation that [[Barbara Geddes]] also makes in ''Paradigms and Sand Castles''),<ref name=":0">{{Cite book|last=Geddes|first=Barbara|title=Paradigms and Sand Castles: Theory Building and Research Design in Comparative Politics|publisher=University of Michigan Press|year=2003|isbn=978-0-472-09835-4|pages=129–139|doi=10.3998/mpub.11910|jstor=10.3998/mpub.11910}}</ref> because few observations make it harder to estimate multiple causal effects, as well as increase the risk that there is [[Observational error|measurement error]], and that an event in a single case was caused by random error or unobservable factors.<ref name=":3" /> KKV sees [[Process tracing|process-tracing]] and qualitative research as being "unable to yield strong causal inference" because qualitative scholars would struggle with determining which of many intervening variables truly links the independent variable with a dependent variable. The primary problem is that qualitative research lacks a sufficient number of observations to properly estimate the effects of an independent variable. They write that the number of observations could be increased through various means, but that would simultaneously lead to another problem: that the number of variables would increase and thus reduce [[Degrees of freedom (statistics)|degrees of freedom]].<ref name=":02"/> Christopher H. Achen and Duncan Snidal similarly argue that case studies are not useful for theory construction and theory testing.<ref>{{Cite journal|last1=Achen|first1=Christopher H.|last2=Snidal|first2=Duncan|date=1989|title=Rational Deterrence Theory and Comparative Case Studies|url=https://www.jstor.org/stable/2010405|journal=World Politics|volume=41|issue=2|pages=143–169|doi=10.2307/2010405|jstor=2010405|s2cid=153591618 |issn=0043-8871|url-access=subscription}}</ref>

The purported "degrees of freedom" problem that KKV identify is widely considered flawed; while quantitative scholars try to aggregate variables to reduce the number of variables and thus increase the degrees of freedom, qualitative scholars intentionally want their variables to have many different attributes and complexity.<ref>{{Cite web|last=Bennett|first=Andrew|editor1-first=Janet M|editor1-last=Box-Steffensmeier|editor2-first=Henry E|editor2-last=Brady|editor3-first=David|editor3-last=Collier|date=2008-08-21|title=Process Tracing: a Bayesian Perspective|url=https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199286546.001.0001/oxfordhb-9780199286546-e-30|access-date=2021-02-19|website=The Oxford Handbook of Political Methodology|language=en|doi=10.1093/oxfordhb/9780199286546.001.0001|isbn=9780199286546}}</ref><ref name=":7" /> For example, James Mahoney writes, "the Bayesian nature of process of tracing explains why it is inappropriate to view qualitative research as suffering from a small-N problem and certain standard causal identification problems."<ref>{{Cite journal|last=Mahoney|first=James|date=2016-09-02|title=Mechanisms, Bayesianism, and process tracing|url=https://doi.org/10.1080/13563467.2016.1201803|journal=New Political Economy|volume=21|issue=5|pages=493–499|doi=10.1080/13563467.2016.1201803|s2cid=156167903|issn=1356-3467|url-access=subscription}}</ref> By using [[Bayesian probability]], it may be possible to makes strong causal inferences from a small sliver of data.<ref name=":22">{{Cite web|last=Bennett|first=Andrew|editor1-first=Janet M|editor1-last=Box-Steffensmeier|editor2-first=Henry E|editor2-last=Brady|editor3-first=David|editor3-last=Collier|date=2008|title=Process Tracing: a Bayesian Perspective|url=https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199286546.001.0001/oxfordhb-9780199286546-e-30|url-status=live|website=The Oxford Handbook of Political Methodology|language=en|doi=10.1093/oxfordhb/9780199286546.001.0001|isbn=9780199286546|archive-url=https://web.archive.org/web/20140804121534/http://www.oxfordhandbooks.com:80/view/10.1093/oxfordhb/9780199286546.001.0001/oxfordhb-9780199286546-e-30 |archive-date=2014-08-04 }}</ref><ref>{{Cite book |last1=Fairfield |first1=Tasha |url=https://books.google.com/books?id=kHB3EAAAQBAJ |title=Social Inquiry and Bayesian Inference |last2=Charman |first2=Andrew E. |date=2022 |publisher=Cambridge University Press |isbn=978-1-108-42164-5 |language=en}}</ref>

KKV also identify inductive reasoning in qualitative research as a problem, arguing that scholars should not revise hypotheses during or after data has been collected because it allows for ad hoc theoretical adjustments to fit the collected data.<ref>{{Cite book|last1=King|first1=Gary|url=https://books.google.com/books?id=A7VFF-JR3b8C|title=Designing Social Inquiry: Scientific Inference in Qualitative Research|last2=Keohane|first2=Robert O.|last3=Verba|first3=Sidney|date=1994|publisher=Princeton University Press|isbn=978-1-4008-2121-1|pages=20–22|language=en}}</ref> However, scholars have pushed back on this claim, noting that inductive reasoning is a legitimate practice (both in qualitative and quantitative research).<ref>{{Cite journal|last=Yom|first=Sean|date=2015|title=From Methodology to Practice: Inductive Iteration in Comparative Research|url=https://doi.org/10.1177/0010414014554685|journal=Comparative Political Studies|language=en|volume=48|issue=5|pages=616–644|doi=10.1177/0010414014554685|s2cid=143936902|issn=0010-4140|url-access=subscription}}</ref>

A commonly described limit of case studies is that they do not lend themselves to generalizability.<ref name=":3" /> Due to the small number of cases, it may be harder to ensure that the chosen cases are representative of the larger population.<ref name=":19" />

As small-N research should not rely on random sampling, scholars must be careful in avoiding selection bias when picking suitable cases.<ref name=":6" /> A common criticism of qualitative scholarship is that cases are chosen because they are consistent with the scholar's preconceived notions, resulting in biased research.<ref name=":6" /> Alexander George and Andrew Bennett also note that a common problem in case study research is that of reconciling conflicting interpretations of the same data.<ref name=":7" /> Another limit of case study research is that it can be hard to estimate the magnitude of causal effects.<ref>{{Cite book|last=Gerring|first=John|url=https://books.google.com/books?id=xECY0nnkTvMC|title=Case Study Research: Principles and Practices|date=2007|publisher=Cambridge University Press|isbn=978-0-521-85928-8|pages=44, 53–55|language=en}}</ref>

==Teaching case studies==
Teachers may prepare a case study that will then be used in classrooms in the form of a "teaching" case study (also see [[case method]] and [[casebook method]]). For instance, as early as 1870 at [[Harvard Law School]], [[Christopher Langdell]] departed from the traditional lecture-and-notes approach to teaching [[contract law]] and began using cases pled before courts as the basis for class discussions.<ref>{{cite book | last=Kimball | first=Bruce A. | title=The Inception of Modern Professional Education: C. C. Langdell, 1826–1906| publisher=University of North Carolina Press | publication-place=Chapel Hill | date=2009 | isbn=978-0-8078-3257-8 | oclc=261174163 |pages=[https://books.google.com/books?id=Q2PAHnJ41c4C&pg=PA143 143-444]}}</ref> By 1920, this practice had become the dominant pedagogical approach used by [[law schools in the United States]].<ref>{{cite journal|last1=Jackson|first1=Giles|year=2011|title=Rethinking the case method|journal=Journal of Management Policy and Practice|volume=12|issue=5|pages=142–64}}</ref> 
[[File:Case Study Caption 1.jpg|thumb|right|200px|Engineering students participate in a case study competition.]]

Outside of law, teaching case studies have become popular in many different fields and professions, ranging from business education to science education. The [[Harvard Business School]] has been among the most prominent developers and users of teaching case studies.<ref name="Garvin">{{cite journal|last1=Garvin|first1=David A.|year=2003|title=Making the Case: Professional Education for the World of Practice|url=http://www.hbs.edu/faculty/Pages/item.aspx?num=15306|journal=Harvard Magazine|volume=106|issue=1|pages=56–107}}</ref><ref name="Ellet">{{cite book|last=Ellet|first=W.|url=https://archive.org/details/casestudyhandboo00elle|title=The Case Study Handbook: How to Read, Write, and Discuss Persuasively about Cases|publisher=Harvard Business School Press|year=2007|isbn=978-1-422-10158-2|location=Boston, MA|url-access=registration}}{{page needed|date=December 2017}}</ref> Teachers develop case studies with particular learning objectives in mind. Additional relevant documentation, such as financial statements, time-lines, short biographies, and multimedia supplements (such as video-recordings of interviews) often accompany the case studies. Similarly, teaching case studies have become increasingly popular in science education, covering different biological and physical sciences. The National Center for Case Studies in Teaching Science has made a growing body of teaching case studies available for classroom use, for university as well as secondary school coursework.<ref name="Palmer2015">{{Cite book |title=Case Based Teaching and Learning for the 21st Century |last1=Palmer |first1=Grier |date=2015-01-01 |publisher=Libri |isbn=9781909818569 |location=Faringdon |pages=19–38 |last2=Iordanou |first2=Ioanna |editor-last=Courtney |editor-first=Nigel |chapter=Exploring Cases Using Emotion, Open Space and Creativity |access-date=2024-09-27 |editor-last2=Poulsen |editor-first2=Christian |editor-last3=Stylios |editor-first3=Chrysostomos |chapter-url=https://www.researchgate.net/publication/282291120}}</ref><ref name="NCCSTS">{{cite web|title=About Us|url=http://sciencecases.lib.buffalo.edu/cs/about/|access-date=2018-09-12|website=National Center for Case Study Teaching in Science (NCCSTS)|publisher=University at Buffalo|editor-first1=Clyde F.|editor-last1=Herreid|editor-first2=Nancy A.|editor-last2=Schiller|editor-first3=Carolyn|editor-last3=Wright|editor-first4=Ky|editor-last4=Herreid|archive-date=2018-09-13|archive-url=https://web.archive.org/web/20180913002426/http://sciencecases.lib.buffalo.edu/cs/about/|url-status=dead}}</ref>

==See also==
* [[Analytic narrative]]
* [[Casebook method]]
* [[Case method]]
* [[Case competition]]
* [[Case report]]
* [[Process tracing]]

==References==
{{Reflist|30em}}

==Further reading==
* {{cite journal|last1=Baskarada|first1=Sasa|title=Qualitative Case Study Guidelines|url=https://nsuworks.nova.edu/cgi/viewcontent.cgi?article=1008&context=tqr|date=October 19, 2014|journal=The Qualitative Report|volume=19|issue=40|pages=1–25|ssrn=2559424}}
* Bartlett, L. and Vavrus, F. (2017). ''Rethinking Case Study Research.'' Routledge.
* {{cite journal |last1=Baxter |first1=Pamela |last2=Jack |first2=Susan |year=2008 |title=Qualitative Case Study Methodology: Study Design and Implementation for Novice Researchers |journal=The Qualitative Report |volume=13 |issue=4 |pages=544–59 |url=http://nsuworks.nova.edu/tqr/vol13/iss4/2 }}
* {{cite journal |doi=10.2307/258557 |jstor=258557 |title=Building Theories from Case Study Research |journal=The Academy of Management Review |volume=14 |issue=4 |pages=532–50 |year=1989 |last1=Eisenhardt |first1=Kathleen M. |author-link=Kathleen M. Eisenhardt }}
* George, Alexander L. and Bennett, Andrew. (2005) ''Case studies and theory development in the social sciences''. MIT Press. {{ISBN|0-262-57222-2}}
* Gerring, John. (2008) ''Case Study Research''. New York: Cambridge University Press. {{ISBN|978-0-521-67656-4}}
* {{cite journal | last1 = Kyburz-Graber | first1 = Regula | year = 2004 | title = Does case-study methodology lack rigour? The need for quality criteria for sound case-study research, as illustrated by a recent case in secondary and higher education | journal = Environmental Education Research | volume = 10 | issue = 1| pages = 53–65 | doi = 10.1080/1350462032000173706 | s2cid = 218499108 }}
* {{cite book |editor1-last=Mills |editor1-first=Albert J. |editor2-first=Gabrielle |editor2-last=Durepos |editor3-first=Elden |editor3-last=Wiebe |title=Encyclopedia of Case Study Research |publisher=SAGE Publications |year=2010 |isbn=978-1-4129-5670-3 }}
* Ragin, Charles C. and Becker, Howard S. Eds. (1992) ''What is a Case? Exploring the Foundations of Social Inquiry''. Cambridge University Press. {{ISBN|0-521-42188-8}}
* Scholz, Roland W. and Tietje, Olaf. (2002) ''Embedded Case Study Methods. Integrating Quantitative and Qualitative Knowledge''. Sage. {{ISBN|0-7619-1946-5}}
* Straits, Bruce C. and Singleton, Royce A. (2004) [https://web.archive.org/web/20080528061240/http://www.oup.com/us/catalog/general/subject/Sociology/TheoryMethods/?view=usa&ci=0195147944 ''Approaches to Social Research''], 4th ed. Oxford University Press. {{ISBN|0-19-514794-4}}.
* {{cite book |first=Gary |last=Thomas |title=How to Do Your Case Study: A Guide for Students and Researchers |publisher=SAGE Publications |year=2011 }}
* {{cite book
 | last1 = Yin | first1 = Robert K
 | title = Case study research: design and methods
 | edition = 6th
 | date = October 2017
 | publisher = SAGE Publications
 | location = Thousand Oaks, California, US
 | isbn = 978-1-5063-3616-9
}}

==External links==
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