Forum Archive : Terminology

"Equity", "volatility", "claim", "market"

From:   Erik Gravgaard
Address:   erikg@inet.uni-c.dk
Date:   5 June 1995
Subject:   Re: glossary needed
Forum:   rec.games.backgammon
Google:   3qv28i$htm@news.uni-c.dk

John B Kelly wrote:
>     I've read the FAQ, a couple of backgammon books, and this
> news group for quite awhile, and there are still some words I
> don't quite understand.  And I bet some other readers might like
> these words clarified.  It might also be a good idea to talk
> about them in the FAQ.  The terms are EQUITY, when it is paired
> with other words like shot equity, racing equity, cubeless
> equity, match equity, etc; VOLATILITY, often used as low or high
> volatility regarding a position and whether to double; CLAIM,
> which refers I think to the point when someone should double, but
> I'm not sure; MARKET, as in having a market or losing one's
> market, again referring to the precise moment to double; if I
> remember correctly: LOW VARIANCE, which I have no idea what that
> meant.

I'll give it a try. Some of my explanations might not be accurate
enough, and they might not even be correct, but I am sure that errors
will be corrected be the many experts.


The easy explanation is that it is VALUE. Meaning that the equity in a
position will be a number (positive if you are the favourite, and your
opponent will in that case have the negative value as his equity, as
it has to add up). The number (for instance + 0,655) represents the
number of net points your position is worth. The calculation is made
by multiplying the probabilities of an occurence with the appropriate
number of points won or lost, and then adding all the values together
to reach the final net value, the Equity.


As I see it, it depends on the context, but I suppose that it often
relates to the shot probability. It could however also be the equity
(as described above), when only looking at the immidiate or long term
shoot possibilities.


The equity (as described above), when only looking at the non contact
game. Usually one would try to seperate the assessments (Shot E. and
Racing E.) and then add them up afterwards. Mostly because it makes
the mental task easyer.


Simply a question of setting the goal line. In equity (as described
above) one looks at one game only, and the equity is points as the
goal should be to win as many points as possible.

But when you are playing a match your goal is not to win as many
points as possible (for instance in a 5 point match it doesn't matter
if you win 16-0 or 5-4) instead you are aiming at winning the match -
and just that.

So now your equity is all about the match winning chances, and your
equity will be a value between 0 and 1.


Does only apply when we are dealing with a match. In this case for
different reasons the cube might have lost it's potential (for
instance at match score 4-4 to 5 or 3-3 to 5 with the cube allready on
"2"). In these cases the game will have to played to the end as the
cube cannot end the game.

Again one could try to seperate the calculations and first try to view
the position "cubeless" as it does simplify the assessment somewhat,
and then afterwards one could try add or correct for the cube and the
influence the cube has (if it is still alive).


The nature of the position. In other words: How likely is it to see a
big swing in the position, making a big difference in the equity on
the next rolls (for both players). Normally the volatility is an issue
when deciding to double or not.

As one would like to double at the optimal point giving the maximum
effect with the minimum risk, it is important to look out for how
likely it is that you might loose your market (see below) and by how
much. With a high volatility one would double earlier than with a low
volatility, where you would try to make your slow advance to the
optimal point of doubling.


You are claiming when you are offering a double, that your opponent
should drop (or at least he should drop in your view).

Normally one would talk about claiming when estimating to play on for
the gammon vs. claiming.


To loose your market is to miss the chance of your opponent to take
the cube (accept the doubling). As stated above you would like to
offer the best possible double (the one that hurts your opponent the
most), but in the attempt you might "wait too long" so that your
opponent has an "easy drop".

Normally one would try to look for "Market Loosers" when one is
thinking about not doubling. If you can find no Market Loosers (and
remember that you should look at both your own roll and your
opponents) you can wait with the doubling as you have lost nothing by
not doubling - with no Market Loosers" you can allways double at the
next turn (if it still looks favourable).

Erik Gravgaard
Pres. of the Danish
Backgammon Federation
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