Sunday, August 12, 2007


Selection Bias And Result-Oriented Thinking (1)

A couple of recent thread on 2+2 have started me thinking on these ever-popular topics. The first one combines the two themes quite nicely

A new breed of fish are on the way if this guy keeps teaching !

Unfortuately the video has been taken off YouTube "by the user". Presumably out of embarrassment. What happened was, he was in a two-table Sit and Go, limped with Q9, saw the flop 3-handed which was KTx, checked around, the turn came a Jack, and the original UTG limper pushed all-in. Now this was a teaching video with the hero expaining his thought process. It is a shame that it's not up any more because you'll just have to take my word for it that from a starting point of "Well I don't think he has AQ because he didn't raise pre-flop", the hero managed to find and justify a fold. Comments proceeded along the predctable path of ZOMG what a donk, with the most apposite comment IMO being "OH MOTHER [censored] FFS JUST [censored] CALL YOU ASSHAT". Quite.

Then someone, who obviously knows the guy who made the video, rode over the horizon to his defence :

"One thing about Full Tilt though is that the outdraws are completely outrageous there, so I can't really blame him ... He did after all win that tournament"

later following up with

"The reason I am holding judgement here is that MartyS showed us a video where he won 2 MTT tournaments on Party side by side - not just final table, but FIRST place, both of them!!"

O RLY. Selection bias much ? I'm going to throw a question out in the dark here. Did he show you any videos where he folded the second nuts "to wait for a better spot", and then lost a coin flip 3 hands later ? Or got blinded off and finished third ? Did he show you any videos where he finished 158th in 2 MTT tournaments on Party side by side ? I'm going to guess No here. But does that mean those things never happened ? How many teaching videos didn't make the cut ?

The rationale of "and I went on to win the tournament" in justification of a play is an old favourite on the forums. Of course, on a moment's thought, it's bollocks. Winning a tournament does not imply that you played every hand correctly. When you combine this with the post facto selection bias of someone picking a tournament or two out of probably hundreds available to him to make into a teaching video, it really is beyond ridiculous.

Finally, to a lesser extent, this is something you have to watch out for on PokerXFactor and the like. Most people just don't bother uploading a tournament in which they finished 77th. Why would they ? So sometimes you have to be careful, even with the better players. Make sure you check how many coin-flips, or even underdog hands, they actually won, before unconditionally adopting their style. In the end, you just have to use your own judgement about individual hands, and results be damned. Tune in later for Part 2, which features the ever-controversial Phil Hellmuth !

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