P(Cavity | toothache catch)
= α · P(toothache catch | Cavity) P(Cavity)
= α · P(toothache | Cavity) P(catch | Cavity) P(Cavity)

n This is an example of a naïve Bayes model:
P(Cause,Effect1, … ,Effectn) = P(Cause) πiP(Effecti|Cause)
n Total number of parameters is linear in n