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Comment by marek_sklenka on Analysis of a Secret Hitler Scenario · 2019-08-23T17:08:35.528Z · LW · GW

I agree with the qualitative analysis and the conclusion but I got different answers when I did the same calculations.

So given that Marek had accused Sam that meant that Marek was a liberal with probability 75%.

I think the correct probability here is 2/3, not 75%.



P(accuse)=37.5% because if I am liberal I only accuse Sam if he is fascist (50% of the time) and if I am fascist I accuse only when I am bold and Sam is liberal (25% of the time).

Imagine 100 games are played. Sam gets accused in 37.5 games. Marek is liberal in 25 of those games.

I had a belief that Marek was Fascist with probability about 50% but I should have already updated to ~88% that he was a fascist as opposed to an unlucky liberal (100% of the time he didn't draw 3 fascist articles he buried a liberal and is a fascist and half the rest of the time he's a fascist by my prior).

Using Bayes' theorem and 23% as the probability of drawing 3 fascist policies, I got 81.3% (and not 88%) as the accurate probability that Marek is fascist.


Comment by marek_sklenka on Analysis of a Secret Hitler Scenario · 2019-08-23T06:38:50.194Z · LW · GW

Another thing to consider is that fascists sometimes intentionally pass a liberal policy to confuse others. This is especially true of Hitler who wants to appear liberal so that he can later be elected chancellor.