NOISY-OR: A Common Simple Model Form

• Earthquake and Burglary are “independently cumulative” causes of Alarm

  • E causes A with probability p1
  • B causes A with probability p2
  • the “independently cumulative” assumption saysProb(A | E, B) = p1 + p2 - p1p2
  • in addition, Prob(A | E, ~B) = p1, Prob(A | ~E, B) = p2
  • finally a “spontaneous causality” parameter Prob(A | ~E, ~B) = p3

• A noisy-OR model with M causes has M+1 parameters while the full model has 2M

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