Case Study: Logic

Case Study: Methods and Analysis
could serve. Their treatments differed, however, in
that Lijphart relied greatly on statistical concepts and
language. He was thus skeptical of the value of single
case studies for building social science theories, and,
consistent with the widespread preference at the time
for ‘large N’ over ‘small n’ methods, he urged researchers
to consider several means of either decreasing
the number of variables in their models or
increasing the number of cases to be studied in order to
make use of statistical rather than case study methods.
This advice, however, raised the risk ‘conceptual
stretching’ (Sartori 1970), or of lumping together
dissimilar cases under the same definitions. Possibly
for this reason, Lijphart later placed greater emphasis
instead on the controlled comparison of most similar
to cases as a basis for causal inference (Lijphart 1975,
Collier 1993).
Eckstein, in contrast, focused on the use of case
studies for theory testing and argued that even single
case studies could provide tests that might strongly
support or impugn theories. In so doing, Eckstein
developed the idea of a ‘crucial case,’ or a case that
‘must closely fit a theory if one is to have confidence in
thetheory’svalidity,or,conversely,mustnotfitequally
well any rule contrary to that proposed’ (Eckstein
1975, his emphasis). Eckstein argued that true crucial
cases are rare, so he pointed to the alternative of ‘most
likely’ and ‘least likely’ cases. A most likely case is one
that is almost certain to fit a theory if the theory is true
for any cases at all. The failure of a theory to explain
a most likely case greatly undermines our confidence
in the theory. A least likely case, conversely, is a tough
test for a theory because it is a case in which the theory
makes only a weak prediction. A theory’s ability to
explain a least likely case is strong evidence in favor of
the theory. In this way, Eckstein argued, even single
case studies could greatly increase or decrease our
confidence in a theory or require that we alter its scope
conditions.
Alexander George (1979a, 1979b) further developed
case study methods by refining ‘within-case’
analysis and cross-case comparisons in ways that help
each method compensate for the limits of the other.
George argued, as Mill himself had, that the ‘method
of difference’ and the corresponding practice of comparison
of most similar cases could lead to spurious
inferences. One reason for this is that no two nonexperimental
cases achieve the ideal of being similar in
all respects but one independent variable and the
outcome. Thus, there is always the danger that left-out
variables or residual differences in the values of the
independent variables account for the difference in
the outcomes of similar cases of (see Human–
Enironment Relationship: Comparatie Case Studies).
In addition, as Mill recognized, phenomena might be
characterized by what general systems theorists have
termed ‘equifinality,’ or the condition in which the
same outcome can arise through different causal
pathways or combinations of variables. Thus, there
might be no single necessary or sufficient variable for a
phenomenon: it might be that either ABC or DEF
causes Y, and that none of the variables A–F is itself
sufficient to cause Y (see Human–Enironment Relationship:
Comparatie Case Studies). In such circumstances,
pair-wise comparisons of cases might wrongly
reject variables that contribute to the outcome of
interest in conjunction with some contexts but not
with others, and might also accept as causal variables
that are in fact spurious.
To compensate for these limits of controlled comparison,
George developed the ‘within case’ methods
of ‘congruence testing’ and ‘process tracing’ as means
of checking on whether inferences arrived at through
case comparisons were spurious (see Pattern Matching:
Methodology). In congruence testing, the researcher
checks whether the prediction a theory makes
in a case, in view of the values of the case’s independent
variables, is congruent with the actual outcome in the
case. In process tracing, the researcher examines
whether the causal process a theory hypothesizes in a
case is in fact evident in the sequence and values of the
intervening variables in that case. Thus, process
tracing might be used to test whether the residual
differences between two similar cases were causal or
spurious in producing a difference in these cases’
outcomes. Process tracing can perform a heuristic
function as well, generating new variables or hypotheses
on the basis of sequences of events observed
inductively in cases.
George (1979a, 1979b) also systematized case study
procedures by developing what he called the method
of ‘structured focused comparison.’ In this method,
the researcher systematically: (a) specifies the research
problem and the class of events to be studied; (b)
defines the independent, dependent, and intervening
variables of the relevant theories; (c) selects the cases
to be studied and compared; (d) decides how best to
characterize variance in the independent and dependent
variables; and (e) formulates a detailed set of
standard questions to be applied to each case. In
addition, consistent with his emphasis on equifinality,
George argued that case studies could be especially
useful in developing what he called ‘typological
theories,’ or contingent generalizations on ‘the ariety
of different causal patterns that can occur for the
phenomena in question … [and] the conditions under
which each distinctie type of causal patterns occurs’
(George 1979a, his emphasis). He thus advocated a
kind of ‘building block’ approach to the development
of theories in which each case, while rendered in terms
of theoretical variables, might prove to be a distinctive
causal pathway to the outcome of interest.
In the 1980s and 1990s, thousands of books and
articles made use of these improvements in case study
methods in a wide variety of social science research
programs.Meanwhile,scholarscontinuedto elaborate
case study methods and articulate the ways in which
they differed from statistical methods. David Collier,
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