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Charting tells you the past, not the future

22 November 2011

I'm a very patient person, and a very patient gambler in many respects.

I'm patient enough to practice blackjack and video poker strategies on the computer, and patient enough to stick to the strategies in the casino. I'm patient enough to wait for the count to turn favorable before raising my blackjack bets, regardless of whether I've been winning or losing. I'm patient enough to refrain from playing video poker until I find machines with the pay tables I'm looking for.

But charting craps tables? It tries my patience.

Over the years, a number of players have told me about charting results, looking for streaks or trends before they play. I've always responded that streaks are in the past, that they don't tell us what's coming in the future. Charting tables can't help us win.

I did a little survey a number of years ago that did require some patience, time and effort, one that involved charting results for most of a year. It came at a time when I was getting a number of letters — yes, old snail mail, hand-written, pen-on-paper letters — telling me there was something mystic about a hot table, that there's something about the game that transcends the odds.

Games with a fixed mathematical edge in favor of the house — nearly all casino games — are said to have a "negative expectation" for the player. That's shorthand for saying that in the long run, nearly all players will lose money. Craps is a game with a negative expectation. The 1.41% house edge on the pass line gives the player a reasonable chance to win at any one session, but in the long run the house will be the winner, taking an average of \$1.41 for every \$100 wagered.

Still, enough players told me that you can make money at craps by spotting hot tables that I decided to try a little experiment. Several players had told me to wait until the shooter has made two passes in a row, then jump in.

No one has ever been able to explain just why such a table should stay hot. The dice don't know how many passes have been made. It's the table games equivalent of the old slot players' dilemma — would you rather play a machine that has been hitting because it's hot, or one that has been cold because it's due? The answer: It makes no difference, just as the last roll of the dice has no effect on the upcoming roll.

But players like a hot table, so I ran a little check. Actually, it was more of a big check — it took nearly a year. Whenever I was in a casino, in my home state of Illinois or in Nevada, I stopped by a craps table, waited until I saw two consecutive passes, then tracked the result of the next decision. And I also waited until there were two consecutive don't passes and tracked the next result of that sequence. I charted until I had 1,000 trials each way — not as good a sample as a million-hand computer run, but a lot more time-consuming.

The result: Pass bettors won 489 wagers and lost 511 on the next sequence after two consecutive wins. That's close enough to the mathematical expectation of 493 wins and 507 losses that we can say the percentages held up in this trial.

The more trials, the closer you'll come to the expected percentages, and 1,000 trials is really too short a test to be statistically significant. Still, there was nothing here to indicate that hot tables stay hot.

Looking at the results on the two-pass trial the other way, there's little to encourage don't pass bettors, either. Among the 1,000 rolls, the number 12 came up 37 times, meaning that of the 511 losses for pass bettors, the don't players only pushed rather than won on 37 of them. That left don't bettors with 474 wins and 493 losses.

The expectation for 967 decisions would be that don't bettors would win 476 times. On the average, 12 will show 31 times per 1,000 come-out rolls. The resulting few extra pushes left don't bettors slightly behind expectation. Again, the difference is not statistically significant.

Likewise, trials starting with two don't passes showed no particular advantage to a table charter. The dice passed 496 times in those 1,000 trials — just three more passes than the expected average. There were only 28 rolls of 12 on this test, so don't players won 476 bets and lost 496, slightly below their expectation of 479 wins per 972 trials.

Not all trials of this length will work out quite so neatly. Notice that in both tests, pass bettors lost more often than they won, and so did don't pass bettors. That's not guaranteed to happen in every 1,000-trial run. There often will be winners in tests that short.

But don't expect charting to uncover great opportunities. Ultimately, it will tell you only what has been, not what will be.

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Best of John Grochowski
John Grochowski

John Grochowski is the best-selling author of The Craps Answer Book, The Slot Machine Answer Book and The Video Poker Answer Book. His weekly column is syndicated to newspapers and Web sites, and he contributes to many of the major magazines and newspapers in the gaming field, including Midwest Gaming and Travel, Slot Manager, Casino Journal, Strictly Slots and Casino Player.

Listen to John Grochowski's "Casino Answer Man" tips Tuesday through Friday at 5:18 p.m. on WLS-AM (890) in Chicago. Look for John Grochowski on Facebook and Twitter @GrochowskiJ.