Thursday, May 7, 2009

Shuffle up and deal

Have you ever had a Royal Flush? It's exciting, isn't it?

Dbcooper has just blogged about Royal Flushes in a post he calls Great Hands. He asks don't they seem to happen more often in online play than in real-life play?

A Royal Flush is supposed to happen one time out of ~650,000 hands according to Cardgrrl here. In her comments she says that they occur more online than in person because the hands are dealt more quickly, so you see more hands online per the same time frame. She also points out that online you may be multi-tabling. All this is true.

When the ACBL first began using computer-dealt hands at bridge tournaments, players complained there was a high incidence of freak hands. Studies were done and it was determined that the computer-dealt hands were the equivalent of what you would expect from a proability standpoint. They found that when players shuffled the boards by hand, however, they didn't do a good job of mixing the cards. They would give the deck three or four riffles and deal the cards. It's been shown that to get a true shuffle, you should riffle them seven or more times. So, the players who complained of freaks thought so because they were used to seeing blah hands where the defenders' cards always divided evenly, nobody ever had eight-card suits, etc. You can read more about all that here, if your eyes don't glaze over first.

In a casino, the dealers are supposed to riffle twice, then do what is called a strip, then repeat for a total of seven or more times. (This is for a used deck. For a new deck, they do something called wash the cards.) More and more casinos are using automatic shufflers which I assume have been tested and do a good job. But, the dealers who still shuffle by hand don't do it seven times, I can assure you. I'd say four or five is about the most you'll see. Further, there is something called clumping (where cards stick together and are not intermixed properly) that adds to the problem.

Therefore, I am thinking that it is true (for the same amount of hands dealt) that you'll see more "wild" results online. But, they aren't really wild at all. They are what probability says will happen and it is the hand-dealt hands in casinos that are not true results.

1 comment:

  1. I remember when the local (bridge) club first got its duplimate system. There were many complaints about the number of voids and singletons, about how the wild distributions favoured the stronger players, and it just wasn't bridge.

    Now, eighteen months later, the thought of not having hand records would horrify them :)