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. 2021 Oct 4;15(10):e0009761. doi: 10.1371/journal.pntd.0009761

Table 1. Types of interactions between the two covariates.

Criterion Interaction
q (X1X2) < Min (q(X1), q(X2)) nonlinearly weakened
Min (q(X1), q(X2)) < q(X1X2) < Max(q(X1), q(X2)) unilaterally nonlinearly weakened
q(X1X2) > Max(q(X1), q(X2)) bilaterally enhanced
q(X1X2) = q(X1) + q(X2) independent
q(X1X2) > q(X1) + q(X2) nonlinearly enhanced