Saturday, August 4, 2018

Deviating From Basic Strategy: Alternate Scenarios (Blackjack)

In my previous post, I looked at whether playing the "wrong" strategy at a blackjack table really affects the other players at the table. I looked at a handful of different "bad" strategies, but in all cases I looked at the fairly standard scenario of 5 players at an 8 deck table. As before, I've used Wizard of Odds' house edge calculator to make sure the simulator is aligned.

I'm using the following house rules, with the only changes being the number of decks and the number of players at the table:

  • 3 to 2 blackjack/no surrender/dealer hits on soft 17/double after split/split up to 4 hands/resplit aces/can not hit split aces
There are a lot of scenarios below, so here's a quick table of contents:
  • 8 decks, 5 players with a "cautious" player who only slightly deviates from basic strategy
  • 8 decks, 2 players, all deviating strategies
  • 2 decks, 5 players, all deviating strategies
  • 2 decks, 2 players, all deviating strategies
As before, all results are over 100,000 hands. First, I was asked to run the same scenario as last time (8 decks/5 players), but with the deviating player only making a slight tweak to basic strategy by staying on 15 and 16 no matter what (like you often see at a real table). I'm calling this the "cautious" strategy.

One Player Plays "Cautious" Strategy

Remember that the house edge should be around -0.5988%. In the middle of the table this "cautious" strategy marginally hurts that player, dropping their house edge to -0.6443%. Everyone else doesn't change at all, with an edge of -0.5940%

At third base, this strategy hurts about the same to the "cautious" player, to the tune of -0.6464%. And it does inflict damage on everyone else, barely, to -0.6231% (barely crossing the threshold of rejecting the null hypothesis with a p-value of 0.0096). So in the end, the "cautious" approach certainly doesn't merit the verbal abuse that other players often inflict on someone playing that way when they stay on 15 or 16.

Erratic Player at Seat 3
8 Decks, 5 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2, 3, 4, 5Basic-0.5988%0.500$0.00
1, 2, 4, 5Basic-0.5940%0.601$0.00
3Cautious on 15/16-0.6443%0.008-$10.22
Erratic Player at Seat 5 ("Third Base")
8 Decks, 5 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2, 3, 4, 5Basic-0.5988%0.500$0.00
1, 2, 4, 5Basic-0.6231%0.100-$5.46
5Cautious on 15/16-0.6464%0.006-$10.71

8 Decks, 2 Players: All Strategies

Some pretty strong patterns emerge when there are only 2 players. The "bad" player hurts themselves to a much larger degree, and also is much more likely to hurt the other "correct" player.

If the erratic player is in Seat 1, the only strategy that doesn't hurt the basic strategy player is "Cautious" and "Never Bust" (for a refresher on each strategy, check the previous post). All other deviations do hurt the other player.

If the erratic player is at third base, all strategies hurt the basic strategy player, to varying degrees. Interestingly enough, the "Assume 10" bad strategy is even worse than someone playing completely randomly in both cases. 

So the takeaway here is if you're alone with one other person playing incorrectly, you might want to change tables. There's not enough "good" strategy to absorb the bad decisions from the other individual.

Erratic Player at Seat 1
8 Decks, 2 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2Basic-0.6252%0.500$0.00
2Basic-0.6444%0.123$0.00
1Cautious on 15/16-0.7090%0.000-$18.86
2Basic-0.6271%0.454$0.00
1Never Bust-0.9271%0.000-$67.93
2Basic-0.6554%0.034-$6.79
1Mimic-1.6319%0.000-$226.52
2Basic-0.6971%0.000-$16.19
1Assume 10-2.0373%0.000-$317.72
2Basic-0.6787%0.001-$12.05
1Drunk-3.8667%0.000-$729.35
Erratic Player at Seat 2 ("Third Base")
8 Decks, 2 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2Basic-0.6252%0.500$0.00
1Basic-0.6561%0.031-$6.95
2Cautious on 15/16-0.7509%0.000-$28.28
1Basic-0.6508%0.061-$5.77
2Never Bust-1.0380%0.000-$92.88
1Basic-0.6617%0.014-$8.22
2Mimic-1.5979%0.000-$218.87
1Basic-0.7124%0.000-$19.63
2Assume 10-2.1041%0.000-$332.76
1Basic-0.6971%0.000-$16.18
2Drunk-3.8930%0.000-$735.26
2 Decks, 5 Players: All Strategies

What about if there are only 2 decks? Inherently, the house's edge is lower from the start if everyone is playing correctly. Over 100,000 hands, the simulator estimates a drop to -0.4996%. That's an expected loss of about $40/hour for someone playing $100 per hand, which isn't bad at all. 

But if someone else is playing erratically? Their influence is amplified significantly. You still won't be in as bad a place as if you were playing with 8 decks, but you definitely feel the effects more of someone playing the wrong strategy.

Interestingly, no matter where the player sits, the "Assume 10" strategy has a diminished effect compared to 8 deck play. This probably is because getting through the deck faster (especially with 5 players) results in this not being as bad a strategy, and is accidentally "correct" more often.

Another interesting result: the random/drunk player absolutely gets crushed if they're in the middle of the pack. So don't be that guy if there aren't many decks in the shoe. 

The effect of less cards goes both ways: it helps you out if you're playing the right way, but it really hurts you if you play poorly. There's more randomness with more cards, which helps lessen any negative impacts of a bad player (but you're in a worse place to begin with).

Erratic Player at Seat 3
2 Decks, 5 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2, 3, 4, 5Basic-0.4996%0.500$0.00
1, 2, 4, 5Basic-0.5873%0.000-$19.72
3Cautious on 15/16-0.6908%0.000-$43.01
1, 2, 4, 5Basic-0.6115%0.000-$25.17
3Never Bust-0.9514%0.000-$101.66
1, 2, 4, 5Basic-0.6287%0.000-$29.05
3Mimic-1.5248%0.000-$230.67
1, 2, 4, 5Basic-0.6081%0.000-$24.40
3Assume 10-1.8155%0.000-$296.07
1, 2, 4, 5Basic-0.5965%0.000-$21.80
3Drunk-9.3579%0.000-$1,993.11
Erratic Player at Seat 5 ("Third Base")
2 Decks, 5 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2, 3, 4, 5Basic-0.4996%0.500$0.00
1, 2, 4, 5Basic-0.6014%0.000-$22.90
5Cautious on 15/16-0.7032%0.000-$45.81
1, 2, 3, 4Basic-0.6256%0.000-$28.36
5Never Bust-0.9595%0.000-$103.47
1, 2, 3, 4Basic-0.6377%0.000-$31.06
5Mimic-1.5254%0.000-$230.81
1, 2, 3, 4Basic-0.5779%0.001-$17.61
5Assume 10-1.8107%0.000-$294.99
1, 2, 3, 4Basic-0.6102%0.000-$24.89
5Drunk-3.6022%0.000-$698.07
2 Decks, 2 Players: All Strategies

Now for the most heightened scenario I ran: 2 decks AND only 2 players. The house edge should be about -0.5585%. If the "wrong" player is in the first seat, then you don't have anything to worry about if they're simply playing cautiously or playing the "Never Bust" strategy. 

But in all other scenarios, the effects are exacerbated once again. The effect to you is only $20-$50 worse over the course of 3 hours, but we can be very certain that there is an effect, with p-values of 0.000 across the board.

Erratic Player at Seat 1
2 Decks, 2 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2Basic-0.5585%0.500$0.00
2Basic-0.5475%0.741$0.00
1Cautious on 15/16-0.6735%0.000-$25.88
2Basic-0.5655%0.340$0.00
1Never Bust-0.7860%0.000-$51.19
2Basic-0.6900%0.000-$29.59
1Mimic-1.5245%0.000-$217.35
2Basic-0.6335%0.000-$16.88
1Assume 10-2.0355%0.000-$332.33
2Basic-0.6715%0.000-$25.43
1Drunk-3.8830%0.000-$748.01
Erratic Player at Seat 2 ("Third Base")
2 Decks, 2 Players
Seat NumberStrategyHouse EdgeP-Value$ Cost vs Base
1, 2Basic-0.5585%0.500$0.00
1Basic-0.6675%0.000-$24.53
2Cautious on 15/16-0.9325%0.000-$84.15
1Basic-0.6675%0.000-$24.53
2Never Bust-0.9325%0.000-$84.15
1Basic-0.5900%0.032-$7.09
2Mimic-1.5960%0.000-$233.44
1Basic-0.8230%0.000-$59.51
2Assume 10-2.3225%0.000-$396.90
1Basic-0.6490%0.000-$20.36
2Drunk-4.0120%0.000-$777.04
Conclusion

In conclusion, if there are a large number of decks and a lot of people, you don't have to worry about someone else not playing basic strategy. The reactions to the contrary are overstated at best and malicious at worst. But if it's just you and one other player who's marching to the beat of their own drum, or that player is at third base, you should probably change tables. This is said with one large caveat: the underlying assumptions to all of this are that you, and the other non-deviating players, are playing basic strategy. If you're trying to count... then this might be a different story.

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