NCA: Necessary Condition Analysis

Performs a Necessary Condition Analysis (NCA). (Dul, J. 2015. Necessary Condition Analysis (NCA). ”Logic and Methodology of 'Necessary but not Sufficient' causality." Organizational Research Methods) NCA identifies necessary (but not sufficient) conditions in datasets. Instead of drawing a regression line ”through the middle of the data” in an xy-plot, NCA draws the ceiling line. The ceiling line y = f(x) separates the area with observations from the area without observations. (Nearly) all observations are below the ceiling line: y <= f(x). The empty zone is in the upper left hand corner of the xy-plot (with the convention that the x-axis is ”horizontal” and the y-axis is ”vertical” and that values increase ”upwards” and ”to the right”). The ceiling line is a (piecewise) linear non-decreasing line: a linear step function or a straight line. It indicates which level of x (e.g. an effort or input) is necessary but not sufficient for a (desired) level of y (e.g. good performance or output).

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