Table 1.

Terms and Definitions of Qualitative Comparative Analysis (QCA)

Term	Definition
Case	A site under study.
Outcome	The result of one or more conditions.
Condition	A factor that is associated with an outcome of interest.
Crisp set	A type of QCA in which conditions are either “present” or “not present” for each case; conditions are coded as 1 or 0, respectively, for each case.
Fuzzy set	A type of QCA in which cases are assigned a value between 0 and 1, based on their degree of membership in the condition. Cases with membership over .5 are considered to be more in than out of a condition, and cases with membership below .5 are considered to be more out than in.
Necessity	A condition is necessary if the condition is present every time the outcome is present.
Sufficiency	A condition (or combination of conditions) is considered sufficient if the outcome is present each time the condition (or combination of conditions) is present.
Calibration	A number that is assigned to a condition to represent a case's degree of membership in that condition.
Calibration structure	A framework devised by researchers that breaks each condition down into tangible measures, and breaks each measure down into fuzzy set values. Clear definitions are created for each fuzzy set value.
Solution pathway	A combination of two or more conditions that is associated with an outcome.
Consistency	A measure of the degree to which cases that follow the same pathway also share the same outcome.
Coverage	A measure of the frequency of a given pathway to an outcome.