 Okasha proposes a test for causal adequacy that works this way: if the first term takes a positive value, then \(W_{k}\) and \(P_{k}\) must be causally related, or else the equation is not causally adequate. Equally, a version of the Price Equation is not causally adequate if its statistical functions take a positive value despite their components failing to be causally related, or if its statistical functions take value zero when their components are causally related. Whether a version of the Price Equation is causally adequate is thus a function of the causal relationships among the variables in the system. On this approach, the concept of causal adequacy means something different than causal interpretability does for equations that exhibit dependencies between variables that represent causes.