Cheng's PowerPC Theory

In Cheng's PowerPC theory^[Cheng], the strength of a causal factor is measured by the difference in conditional probabilities for the effect's occurrence between whether the cause participates or not. In equation form

where $\mathrm{CC}$ is the candidate cause, $E$ is the effect produced, and $P\left(E\right|\mathrm{CC})$ is the probability of $E$ given that $\mathrm{CC}$ has occurred.

Refinements of the theory take into account alternatives, preventions, and the extent of (statistical) independence among these factors.