data envelopment analysis data envelopment analysis

Generally taken to mean an odd unit with an input-output mix that significantly differs from the rest of the units. This can be due to a measurement error, or as a result of the outlier having different operating practices. Outliers that are efficient can introduce bias into the analysis. See Epstein and Henderson (1989). [Epstein …

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A factor which consists of a set of predefined values that are ranked in a specific order. An ordinal variable can be seen as a special case of a categorical variable. If the values of an ordinal factor need to be scaled, the inherent order must be preserved (Cook et al 1993). [Cook W, Kress …

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Bessent et al (1988) coined this term (later simply known as unenveloped units) to refer to those inefficient units that are not fully enveloped by the efficiency frontier. To be fully enveloped in the CCR model, an inefficient DMU needs to have (m+n) -1 reference units where m+n denotes the number of factors. Unenveloped units …

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Same as exogenously fixed factor.

Associated with each DEA model type (eg CCR, BCC) is both a primal and dual formulation. To avoid confusion over which formulation is primal and which dual, the multiplier form is always understood to refer to the formulation involving virtual multipliers (Ali and Seiford 1993). [Ali A and Seiford L (1993), ‘The mathematical programming approach …

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MPSS is a unit (point) on the efficiency frontier that maximises the average productivity for its given input-output mix and after which decreasing returns to scale set in. See Banker & Kemerer (1989) on how to compute the MPSS. [Banker R and Kemerer C (1989) ‘Scale economies in new software development’, IEEE Trans. On Softw. …

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The requirement that the relationship between inputs and outputs not be erratic. Increasing the value of any input while keeping other factors constant should not decrease any output but should instead lead to an increase in the value of at least one output.