Steve Jacobs wrote:
> > Steve Jacobs:
> > > As usual, if the game is negative, then using the double feature
> > > reduces risk. This holds for all size payoffs.
> >
> > I'll venture a question here, Steve.
> >
> > Mind you, I get a little nervous in our discussions these days
> > whenever the word "risk" is floating about. For that matter, I start
> > questioning the agility of my mind once we get going...
> >
> >
> > Simply put, is a 9/6 Jacks player who doubles and redoubles on every
> > win, to jackpot or bust, playing a less risky game than the Jacks
> > player who never doubles?
> >
> > I don't think this is what you suggesting, but it wouldn't be at all a
> > kick to the head if you came back and said you were
>
> The answer might depend on the precise definition of the phrase
> "to jackpot or bust". But, I suspect that is precisely what I'm
> suggesting. Risk works "backwards" in negative games, compared
> to what one would expect from a positive game. The critical question
> is when will you stop doubling in order to cash out and go home.
>
> Suppose you have $1000 in your pocket and you desperately need
> $1100 or else Guido and The Boys will go 9 innings against your
> knees with a baseball bat. The only game is 9/6 JoB with a double
> feature. If you play normal max-EV strategy for 9/6 JoB, and stop
> doubling whenever your total bankroll hits/exceeds the $1100 goal,
> then your knees have a higher probability of going unsmashed if you
> use the double feature. This assumes that the double feature is "fair"
> in that it increases variance while leaving ER unchanged.Well, not to quibble, but technically I think it would be incorrect to
double if it will cause you to exceed goal, as I explain further,
below.
You're partly right. If doubling can't reach the goal, then doubling
is correct. If doubling exceeds the goal only by a tiny amount, then
doubling can still be the correct thing to do. This holds more for large
payoffs -- if the goal is 9,999 away and you get a 5,000 unit royal,
then doubling gives you a 50/50 shot at reaching the goal right now.
But subject to that -- and to a very small percentage of
exceptions based upon relative stake/goal sizes -- I'm confident that
what you have said is true so long as we have a particular goal.I'll start with what I think are likely exceptions. I don't know what
the curve of a graph would look like, but at some point with a small
enough stake -- relative to your goal -- you do cross the line (which I
mention only academically for the sake of discussion, because such
extremes have little practical application). For instance, JoB-9/6 has
approximately a 45% winning-game rate. If your session stake is only a
single bet, then out of the mere 45% of the time that a normal player
would survive the first vp bet, a player who then doubles has only half
that chance of surviving to bet again.
The real question is whether doubling improves the overall probability of
reaching the goal. Playing the negative game is mathematically equivalent
to flipping a biased coin. It is the bias that hurts you. Doubling is
exactly like removing the bias from the coin for some of the flips.
For example, doubling a win of 100 units is like committing to flipping
a _fair_ coin repeatedly until you either win 100 additional units or
suffer a net loss of 100 units. If you forego doubling, but you still need
more than 100 units to reach the goal, then you just conciously chose
to flip a coin that is biased against you instead of flipping a fair coin.
Let me make this more concrete. Say you start with a single unit, and
your goal is 200 units. Your very first play results in a win of 100 units.
If you choose to double, you will have a 50/50 chance of reaching
your goal. If you decide not to double, and you are playing 9/6 JoB,
then based on the "equivalent coin" for this game, your probability of
reaching the goal with your (new) bankroll of 100 units is only 48.97%.
I think this can probably be reduced to a reasonably simple formula
that tells us precisely when to double. I'll try to work out the formula
for this.
If a person has only a 2 bet
stake, it would seem to me that a doubler also has a worse chance of
survival; 55% will lose their first bet on vp before ever reaching the
doubling option; of the 45% who win their first bet on vp, only 22.5%
will win the doubling, although some will now have much more than their
original 2 bet stake. But 77.5% are now down to a single bet remaining,
and if we use the same math, 77.5% of them will also lose their second
bet, so after 2 bets, over 60% will be busted without ANY hope of saving
their knees. Now, in comparison to the regular win-loss rates for the
same game, with a 55% chance of losing each vp game, after two bets,
only 30% will be busted without any hope of saving their knees. I used
a VERY small bankroll just to make it easy for folks to see what I
mean. Now, I don't know where the lines cross on a graph, and I'm not
going to go through that much work for this, but at some point, and no
doubt VERY quickly, as soon as your stake is increased to a certain
point, then it would immediately become advantageous to switch to
doubling all winning hands for as long as your stake does not dip below
that level.
The mathematics for risk is complicated for VP, because the equation is
nonlinear. However, I've studied this enough to say that your intuition
is incorrect. The correctness of doubling isn't a matter of how much you
_have_ but rather it is how much you _need_ to reach the goal. In a
sense, you're approaching the problem from the "wrong end." Suffice
to say that if doubling is correct for a large bankroll, it remains correct
for any smaller bankroll size, right down to a single unit.
Now before going on to my other theory that you would never double if it
will put you beyond your goal, lets take another example of a more
realistic figure. Let's say that you owe Guido $1500.00 and you have a
modest but perhaps somewhat realistic $65.00 in your pocket (in other
words, you have a 52 bet stake on a JoB quarter machine, and you need to
build it into a 1200 bet stake). I had arbitrarily started with an even
50-bet stake ($62.50) but discovered that I could not enter a fraction
of a dollar in Jeff Lotspiech's "Gambler Ruin Calculator", so I bumped
it up to an even $65.00 and then also ran it for an even $60.00 (48
bets). So for this discussion I will speak in terms of 'betting units'
rather than dollars or coins, because it's easier, and when I speaking
about 1, 2, 3, etc., "wins", I am still talking about full-coin such
that 1 win really means 5 quarters.
That's fine, working in units is easier.
On each winning-bet you proposed
doubling until you either bust or your stake exceeds 1000, so that's
what we'll do.
No, with a goal of 1200 units, you would definitely double whenever
winning the double will leave you with less than (or exactly) 1200
units. You'd never double a win that causes you to go far beyond
the goal. You'd sometimes double a win that goes slightly beyond
the goal, but only if the "excess" is a small enough fraction of the
final win.
On your first bet, you need to win 1151 to meet you
goal, with the following expected results:
54.543% of the time you lose the VP bet and never get a chance to double
21.459% of the time you win 1 and must then double-down 11 times with
chances of winning = 1/2048 x the 21.459% = 1/2048*.21459=
0.0001047802734375
12.928% -- you win 2 and d-d 10 times = 1/1024*.12928= 0.00012625
7.445% -- you win 3 and d-d 9 times = 1/512*.07445= 0.00014541015625
1.123% -- win 4 d-d 9 times = 1/512*.01123= 0.00002193359375
1.101% -- win 6 d-d 8 times = 1/256*.01101= 0.0000430078125
1.151% -- win 9 d-d 8 times = 1/256*.01151= 0.0000449609375
0.236% -- win 25 d-d 6 times = 1/64*.00236= 0.000036875
0.011% -- win 50 d-d 5 times = 1/32*.00011= 0.0000034375
0.002% -- win 800 d-d 1 time = 1/2*.00002= 0.00001
Your Total odds of meeting your goal on the first bet is 0.0005366552734375
Your odds of failing and having to bet further is 0.9994633447265625
In all of these cases, the final double is incorrect.
Now, your 'stake' at the end of each "try" will NEVER be bigger than it
is when you start, or else you will have already met your goal and
stopped. This means that your stake is constantly diminishing as you
repeat your attempts, and the amount that you need to meet your goal
constantly increases. The result is that for each bet (assuming the
same size gap between stake and goal), your odds are NEVER going to be
better than the above, although for this particular beginning stake and
goal, they won't get any worse, either.With a stake of 52 bets and odds of failing of 0.9994633447265625 each
time, your chances of ultimately going bust is
0.9724724189488650115689794580225
or a chance of making it of only 0.027527581051134988431020541977496 =
2.75% This compares to a success rate of 3.10% when using what I
presume is max-ER strategy and NEVER doubling. This can be confirmed on
Jeff Lotspiech's Calculator at
http://www.lotspiech.com/GamblersRuin.html -- which I presume is max-ER
-- but you need to be patient since Jeff's calculator needs to run
somewhat over 100K hands to reach at least 3.1% 'retired', and it was
still at that level about 250,000 hands. I would also assume that that
figure could also be improved slightly using your own min-risk strategy,
Steve.
The equivalent coin model says that there is a 3.38% chance of turning
a 52 unit bankroll into 1200 units. The real value is slightly smaller than
this. I have no doubt that correct doubling will improve on the real value.
By the way, the figures when starting with a 48-bet stake ($60.00) are
as follows: using 'doubling', your chances of success drop from 2.75%
to only 2.54%, and with NO doubling, your chances drop from 3.10% to
2.80%, which is still better than the doubling success-rate.
Again, the analysis doesn't match what I'm claiming.
I do agree with a comment that Harry Porter recently made that this
probably doesn't matter as much to folks who are planning to stop
playing when they hit a particular goal;
I think you've got that backwards -- those are exactly the people
who this should matter to.
If they are planning to play a negative game endlessly, then they
are simply planning to lose whatever amount they consider to be
"entertainment value" for the game.
oh, they might stop after a
big win -- for that particular trip -- but if they even return to the
casino again, then in keeping with the concept of just a single session
in life, doubling during parts of their session isn't expected to really
make any difference in the long-run.
Heh. Yes, if you are planning to ensure a long term loss, then slowing
the bleed rate is about all you can hope for. The concept of "risk"
becomes completely meaningless in that scenario, so none of this
discussion applies.
HOWEVER, all of that having been said, your point is well-taken Steve,
and I think you are correct that in the vast marjority of instances
where you have a goal that must be met -- especially with 'Guido and The
Boys' breathing down your back -- it is no doubt best to add doubling.
But I do think that one should use a blend of not-doubling when their
stake is about to bottom-out, but doubling whenever their stake is
'safe' ... but not when doubling will exceed the goal.
You are mistaken in regard to the small stake. That is precisely when
doubling gives the most benefit.
This last point
can be seen quite easily when you are in the situation of hitting a
Royal to bring you within a few dollars of your goal; it would clearly
be insane to double at that point. Instead, you take your winnings and
resuming doubling on the following hands.
Right. But, if doubling a royal will take you to (goal + 1 unit) then it
is clearly correct to double.
···
On Tuesday 17 February 2004 02:13 pm, Bill Velek wrote:
> On Monday 16 February 2004 07:09 pm, Harry Porter wrote:
...