NSCA: Necessary and Sufficient Condition Analysis

Tests and quantifies bivariate statements in which a condition is both necessary and sufficient for an outcome. Necessity and sufficiency are estimated as two empty-space frontiers on diagonally opposite corners of the same scatter plot, using the 'NCA' package of Dul (2016) <doi:10.1177/1094428115584005> for the necessity side and 'SCAtools' for the sufficiency side. The two empty zones and the region between them tile the analytic scope, which yields the reported areas as one identity rather than as separate definitions: a weakest-component effect, a normalised geometric mean of the two components, the share of the scope the claims jointly rule out, and the data zone they still admit. The conjunction is decided by an intersection-union combination of the two directional permutation tests, optionally driven by a single shared permutation sequence so that a statistic of both components can also be tested. These are random-pairing screens rather than direct tests of a causal necessary-and-sufficient relation, no magnitude benchmarks are asserted for the joint indices, and a dual-threshold table separates outcome levels that are out of reach, admitted, or guaranteed. An ordinary least-squares line can be drawn alongside the two frontiers as a central-tendency reference; it is an average-effect summary and is never treated as a component of either claim.

install.packages("NSCA")

Try the NSCA package in your browser