We all know the role that luck plays in the game.
But, assuming that we can rely on the bots (a very reasonable
simplifying assumption in my view), how should we assess
match performance?
The answer is actually blindingly obvious -- simply observe how
much MWC (match-winning-chances) a player sacrifices.

The reasons for introducing much more complex metrics involving
EMG normalization are entirely bogus and spurious.
So a player would get penalized far more for a mistake at DMP than
for the same mistake in the first game. What on earth is wrong with
that? At DMP, it's a more serious mistake. What if the reason for
the DMP mistake is that the player is struggling with the greater tension? Shouldn't that lesser ability to cope with tension be penalized?
Does anyone think tennis is unfair in that the value of a point changes depending on the stage of the match?
I saw a player, who was new to competitive backgammon, run himself
extremely low on time for the final DMP game of his match, so he had
nowhere near enough time to play the final game competently, made
horrible checker blunders and lost it.
He had played the first game slowly. Suppose he'd played the first game super-fast to blunder in that game and been able to play the others at
a reasonable speed. Surely that would have been more sensible (although admittedly still not optimal), and yet the EMG theory does not recognise this. Under this EMG normalization theory, running yourself low on time doesn't get penalized enough.

Paul

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On 7/27/2023 1:37 PM, peps...@gmail.com wrote:

We all know the role that luck plays in the game.
But, assuming that we can rely on the bots (a very reasonable
simplifying assumption in my view), how should we assess
match performance?
The answer is actually blindingly obvious -- simply observe how
much MWC (match-winning-chances) a player sacrifices.

Bob Koca and I argued this point on BGOnline many years ago,
so I basically agree with you.

We got considerable pushback. The counter-argument that I found
to be most reasonable is that if what you're trying to do is to
estimate *how skillful each player is*, then EMG greatly reduces
variance while (probably) introducing only a small amount of bias.

Here's an illustrative example. Suppose that an 11-point match
at some stage reaches 3-away/3-away. Player A blunders horribly
in the first game of the match, but plays very well in the
3-away/3-away game. By MWC standards, Player A plays very well.
But now imagine that, hypothetically, the 11-away/11-away game
and the 3-away/3-away game were switched. You might infer
that in this scenario, Player A would blunder horribly in the
3-away/3-away game but play the 11-away/11-away game very well.
(This is certainly not a watertight inference. There are
psychological factors at play---maybe Player A's blunders are
a function not of the decisions that arise but of "nerves" in
the first game of a match---plus what is "correct" at 3-away/3-away
is not necessarily "correct" at 11-away/11-away. Nevertheless,
I think it's a reasonable supposition.) In this hypothetical
scenario, Player's A's performance is much worse, because
blunders at 3-away/3-away are more costly than at 11-away/11-away.
We could say that Player A was "lucky" that the tough decisions
arose in the first game rather than later on in the match.

In the long run, we expect that this sort of "luck" will even out,
but it could take a lot of matches for that to happen. All those
EMG shenanigans are a form of (biased) variance reduction, to try
to get a more accurate estimate of skill from less data.

I think this argument is reasonable as far as it goes. If you're
trying to award BMAB titles based on performance, then using EMG
is probably going to yield more sensible results---the benefits
of variance reduction probably outweigh the drawbacks of bias,
especially because there probably isn't going to be that much
*systematic* bias (EMG will probably be biased in one direction
for some matches and biased in the other direction for other matches).

On the other hand, this still doesn't give us a good argument for
using EMG for assessing *who played better* in a particular match.
For this, I agree that MWC is still a more logical choice than EMG. Unfortunately, I think that people have gotten so used to EMG that
they will probably balk if MWC and EMG give different answers to
the question of who played better.

---
Tim Chow

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I think it's been posted here before, but JB wrote a seminal paper
on this some years ago (I forget when):

https://www.fortuitouspress.com/emg

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On 7/27/2023 11:46 PM, Simon Woodhead wrote:

I think it's been posted here before, but JB wrote a seminal paper
on this some years ago (I forget when):

https://www.fortuitouspress.com/emg

That is indeed an excellent article, but it doesn't directly address
Paul's point. Jeremy Bagai is still trying to come up with something
which assigns roughly the same weight to "the same error" at different
match scores, but Paul is arguing against that.

Offhand, I'm unable to find the best place where Bob Koca makes the
argument for using MWC (or VRR, variance-reduced result) to determine
who played better in a match, but here's one old BGOnline post where
he makes some relevant comments.

https://www.bgonline.org/forums/webbbs_config.pl?read=173017

---
Tim Chow

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On Friday, July 28, 2023 at 1:26:13 PM UTC+1, Timothy Chow wrote:

On 7/27/2023 11:46 PM, Simon Woodhead wrote:

I think it's been posted here before, but JB wrote a seminal paper
on this some years ago (I forget when):

https://www.fortuitouspress.com/emg

That is indeed an excellent article, but it doesn't directly address
Paul's point. Jeremy Bagai is still trying to come up with something
which assigns roughly the same weight to "the same error" at different
match scores, but Paul is arguing against that.

Offhand, I'm unable to find the best place where Bob Koca makes the
argument for using MWC (or VRR, variance-reduced result) to determine
who played better in a match, but here's one old BGOnline post where
he makes some relevant comments.

https://www.bgonline.org/forums/webbbs_config.pl?read=173017

Thanks for all commenters on this thread.
I haven't read the bgonline forum yet or looked at the Bagai article.
I'm sure I'll look at these soon, though.

The logic of the EMG crowd would seem to make sense though, as well
as my and Tim's view.
In fact I might be close to a somewhat analogous situation this Sunday.

This Sunday I (and some friends) will be at Roehampton, London, spectating
a mens tennis event.
The median world ranking (ATP) of the players at the event is likely to be approx
1500. Given that the world contains approximately 4 billion male humans, this is a very
high standard in my opinion (1500th out of 4 billion).

Despite this type of ranking impressing me, tennis is not as well funded as soccer or basketball etc., and only a few of such players are likely to receive funding and sponsorship.
I'm sure there will be scouting at this event, where those with access to funds (or, more likely, employed by them) will be taking notes on who is worth supporting
financially, and who can benefit more by professional coaching etc.

Now (finally) comes the relevant point that connects with this thread.
As the scouts watch the matches, and look at players with impressive technique,
power, speed and accuracy, will they focus on (or even notice) the scores at which the
impressive rallies are played?
I kind of doubt it. I think that an excellent serve in the first game of a match will
impressive the scouts about (or almost) as much as the same serve at match point.
If my theory is right, then these scouts are adopting the EMG logic.
I don't have a huge amount of evidence for my view but there is some evidence in that
the scoreboard is changed quite rarely --- only once every two games.

Paul

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On 7/28/2023 8:47 AM, peps...@gmail.com wrote:

Now (finally) comes the relevant point that connects with this thread.
As the scouts watch the matches, and look at players with impressive technique,
power, speed and accuracy, will they focus on (or even notice) the scores at which the
impressive rallies are played?
I kind of doubt it. I think that an excellent serve in the first game of a match will
impressive the scouts about (or almost) as much as the same serve at match point.
If my theory is right, then these scouts are adopting the EMG logic.

As far as technical skill is concerned, my guess is the same as yours.

But scouts also look for mental toughness. For that, they may put more
weight on mental toughness at match point than on mental toughness at
set point for the first set.

---
Tim Chow

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On Saturday, July 29, 2023 at 4:04:21 AM UTC+1, Timothy Chow wrote:

On 7/28/2023 8:47 AM, peps...@gmail.com wrote:

Now (finally) comes the relevant point that connects with this thread.
As the scouts watch the matches, and look at players with impressive technique,
power, speed and accuracy, will they focus on (or even notice) the scores at which the
impressive rallies are played?
I kind of doubt it. I think that an excellent serve in the first game of a match will
impressive the scouts about (or almost) as much as the same serve at match point.
If my theory is right, then these scouts are adopting the EMG logic.

As far as technical skill is concerned, my guess is the same as yours.

But scouts also look for mental toughness. For that, they may put more weight on mental toughness at match point than on mental toughness at
set point for the first set.

From the standpoint of an avid spectator at these events who has spoken to some of the
principals but isn't very well informed:

I think it's a two-track process:
The players are observed in competitive play with the scouts ignoring the score and looking
only at tennis ability.
Combined with that, match scores are examined, and reports are available giving the result
of every single point. This match log is scrutinised to see who won the "big points".

Paul

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