Q. For a really bad player, how bad can blackjack get? I see a lot of players making really bad decisions, and I was wondering how much they can hurt themselves.

A. An average blackjack player bucks a house edge of about 2 to 2.5 percent. A basic strategy player cuts that to half a percent or so, more or less, depending on number of decks and other house rules.

Against a really bad player, the house edge soars. The late Peter Griffin explored the extreme in his classic book, "The Theory of Blackjack," and came up with a house edge of 19.01 percent against the world’s worst player.

He assumed a single-deck game in which the dealer stands on all 17s, so what follows isn’t really an upper limit. Someone who plays a multiple-deck game with bad rules piled on --- with 6-5 payoffs on blackjacks heading the list of stinkers --- can spot the house even more than Griffin’s worst case.

To get to that 19.01 percent house edge, the player has to make some pretty awful decisions:

• Always splitting and resplitting 10s. We’re not talking the garden-variety bad player who splits 10s against 5s or 6s, but someone who splits even against 10s or Aces. I’ve not seen many players who do that, but we are talking about extreme cases here.
• Hitting stiffs against small cards. I encountered a player who did this just a few months ago. It was as if the dealer’s up card didn’t exist. He played his own cards, and if he had 16 or less, he was determined to hit, even if the dealer had a 6.
• Standing on stiffs against big cards. This, I see more often --- a player who is afraid to hit 16, even if the dealer shows a 10. Of course, I don’t think I’ve ever seen one who BOTH hits stiffs against small cards and stands on stiffs against the big ones. 
• Standing on small soft hands, from soft 17 on down.
• Never doubling down.  Several years ago, a stranger in a casino approached me and handed me a copy of his system, and it included never doubling down. I kept waiting for the line about never winning money.
• Exception: Doubling on 10 when the dealer shows 10 or Ace.
• Always splitting 4s and 5s.
• Other improper pair splits.
• Improper play of soft 18 and soft 19.

OK, those are some pretty awful plays. I doubt that any of us have seen anyone who does all of that. It takes someone who seems to be determined to be bad to get the house edge all the way up to 19 percent.

But certainly, there are players for whom blackjack is not the best game in the house, players who can take the house edge up to 4, 5, or 6 percent. Their bankrolls would be better off by betting pass or come, or placing the 6 or 8 at craps --- if they could discipline themselves to stay away from the propositions.

A. You know and I know that mistakes by other players will help him sometimes, and they’re not really worth worrying about. In addition, sitting a first base doesn’t really avoid the issue --- sometimes a player’s mistake will enable the dealer to draw a card that beats the table. Sometimes a player’s mistake will leave a card that busts the dealer and wins for the whole table, too, but it’s the tough losses that stick in our selective memories.

As for your bigger issue of whether seat position makes a difference, it can, especially if you’re counting cards in a single-deck or double-deck pitch game, with cards dealt face down. Sitting at third base enables you to see other players’ cards as they’re turned face up after they’ve made their plays. That extra information might lead to changing your hit/stand decision on a close-call hand.

However, sitting at different positions around the table doesn’t change your cards in any predictable way. You get no better cards whether you sit at first base, third, or anywhere in the middle.

A. The key is the effect of card removal on the composition of the remaining deck. Removing one card from a single deck changes the percentages in a single-deck more than it changes a six-deck pack. That effect means we get more blackjacks and double downs play truer with fewer decks.

Let’s say the first card we’re dealt is an Ace. After all, if we’re to get a blackjack the first card must be either an Ace or a 10. In a single deck game, 16 of the other 51 cards are 10 values. That means 31.37 percent of the remaining cards will complete the blackjack. If six decks are in play, removing an Ace means 96 of the remaining 311 cards are 10-values. That’s 30.87 percent, meaning we have a lesser chance of completing our blackjack in a six-deck game than in a single-deck game.

It works the other way, too. If our first card is a 10 value, 7.84 percent of the remaining cards are Aces in a single-deck game, while 7.72 percent are Aces in a six-deck game.

Double downs? Start with 6-5, for example, and 32 percent of the other cards are 10s in single-deck blackjack, and 30.97 percent in six-deck games.

The proportion of cards are the same regardless of number of decks only immediately after a shuffle. Once cards are dealt, the percentages change more rapidly with fewer decks in play.