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Diaconis on Randomness

Posted By: Phil Simborg
Date: Wednesday, 22 May 2013, at 4:55 a.m.

In Response To: Diaconis on Randomness (Chuck Bower)

I have played gin rummy at the same country club for the past 30 years. It is a fairly high-stakes game. A rule was made 30 years ago that it was illegal to deal unless the cards had been shuffled at least 7 times. A very prominent expert stated that if you shuffle them well 7 times you are "assured randomness" and that there is not much point shuffling them any more than that.

I always suspected that this was baloney, and that the more you shuffled the more you randomized the cards, and that 7 times was no magic number or guarantee of anything...all you could say for sure was that 7 was better than 6 and worse than 8.

One day a friend of my brother's played in the game an laughed at our rule. He took a new deck of cards, in order, and shuffled them 7 times. With only a couple of exceptions, the cards were very close to their original order. Of course, he was a card magician, but he was certainly not a cheater or he would not have shown us his skills. But on his own agreement, he let his opponents do all the shuffling the rest of the day.

I watched the video, and though a lot of it bored me to tears, and a lot of it was over my head, I was certainly convinced that the 7-shuffle rule is false.

By the way, I am convinced that even if you shuffle many times, you need to combine that with some cutting of the cards in between to increase randomness.

One of the best gin players in the world took me under his wing many years ago, and he told me that one of the edges he had was remembering what runs were made in the previous hand, as that helped him predict what cards might be coming up, particularly if he was playing an opponent that did not shuffle much or shuffled badly. I worked hard on this skill myself with some success and I still do this when I play with someone who doesn't shuffle well. Is that cheating? I think it is if you intentionally don't shuffle well yourself in order to take advantage of the memory of the previous hand, but if your opponent doesn't shuffle well when it is his turn, I have never had an ethical problem with this ploy.

FYI I first learned important nuances of the game directly from one of the greatest of all time, Oswald Jacoby, and his book, written in the 60's, is still a great study of the game, though of course, not on a par with Sall's. Oswald knew how to stack a deck and just about every other method of cheating...he would never cheat himself but he showed me that you need to know how to do it in order to catch a cheater. At the time, he was sure that he and the Dallas Aces were being cheated by the Italian team in the world bridge championships, but he couldn't prove it. It was proven a few years later and now draconian means are used to prevent cheating at international bridge competitions.

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