# Thread: kortnman: trackjack player expectation and RSO

1. ## kortnman: trackjack player expectation and RSO

In trying to use the Trackjack's player expectation column, I'm trying to understand what's up with RSO (= Rider Splits Optional), which is said to add a .2% advantage. I found a discussion on another forum where someone explained

"It's only about 0.2% addition to EV when the front player (caller) is sacrificing everything. Otherwise it's much less. It certainly doesn't make the game +EV on its own."

So, if I follow that, the .2 +EV assumes you would have played wrong to begin with. If that's the case, I don't see the usefulness of throwing that into the overall "Player Expectation".

Thanks for any clues, esp. if you can confirm whether RSO is only better assuming you'd otherwise "play wrong", so to speak.

2. ## Dog Hand: Sorry for the belated response...

kortnman,

I only today saw your post!

If the front player is betting small (say \$10 flat bet) and you, the back bettor, are betting large (say \$1000 flat bet), and the two of you are working as a team, then having the front player make some "non-BS" splits works to the advantage of your team.

For example, let's say that you're dealt 7-7 vs. X in a 6D, S17, DAS game. Now B.S. says to HIT, and in fact, if we look at these numbers, which I stole from the Wizard of Odds site (see link below), only because I forgot to bring BJA3 to work today ;-), we can see why:

```
Dealer	Player	Stand		Hit		Double		Split DAS
10	7,7	-0.535586	-0.474064	-0.953611	-0.652075
```
.

Since HIT has the highest (in this case, least negative) EV, B.S. says to HIT this hand. For your team, though, that's NOT the best way to play: after all, as a team you've got \$1010 on the felt, and you're looking at a "best-case" EV of -0.474064, so on average your team is going to lose -0.474064*(\$1010) = -\$478.80464... ouch!

However, what if the front man were to violate B.S. and split those 7's? In that case, you (as the big back bettor) would decline to split, so now your team would have \$1010 on one hand of 7 vs. X, and \$10 on another hand of 7 vs. X. Each of these two hands will have an EV that is one-half the Splitting EV of -0.652075: so each will have an EV of -0.3260375, so now your team is looking at an average loss of -0.3260375*(\$1010 + \$10) = -\$332.55825: still not good, but \$156.24639 better than Hitting the original hand.

This is the essence of a "sacrificial split": the front (small-betting) player makes some otherwise weird splits which the back (big-betting) player declines to play.

Of course, on any +EV splits, the big bettor will naturally split as normal: for example, on 8-8 vs. 6.

Now the team's EV will be decided almost entirely by the big bettor's hands: almost as though the front bettor were betting \$0 per round. In that case, the team's EV will improve by about 0.2% due to these sacrificial splits.

Hope this helps!

Dog Hand

3. ## Don Schlesinger: Re: trackjack player expectation and RSO

> In trying to use the Trackjack's player expectation
> column, I'm trying to understand what's up with RSO (=
> Rider Splits Optional), which is said to add a .2%
> advantage. I found a discussion on another forum where
> someone explained

Adding 0.2% e.v. to a game doesn't mean that the game has +0.2 e.v.! It means that the (negative) e.v. of the game is improved by 0.2%.

Am I misunderstanding your question?

Don

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