Luck versus Skill

 Are luck and skill related?

 From: Eskimo Address: peter.backgren@lmf.ericsson.se Date: 25 February 2003 Subject: How much does luck and skill correlate? Forum: rec.games.backgammon Google: MPG.18c5949378993e0989862@news.lmf.ericsson.se

```How much does luck and skill correlate?

When two players are comparable in skill a -5 or -10 in luck rate
(Snowie terms) pretty much decides who wins. I can't find one single
match in my files where I've won at -10 or worse in luck rate unless
I've been at least two levels higher than my opponent. Where the luck
rate is around -2 I've won several matches where I've outplayed my
opponent.

Now let's assume I play a bad move (error, not blunder). For my next
roll my best play would have allowed 7 joker rolls. But with my worse
play, only 5 rolls qualify as jokers. Now, do bots take this into
account?

X to play (3 2)
+24-23-22-21-20-19-------18-17-16-15-14-13-+
| O  O  O  O  O  O |   |                 O |
| O  O  O  O  O  O |   |                   |
|                  |   |                   | S
|                  |   |                   | n
|                  |   |                   | o
|                  |BAR|                   | w
|                  |   |                   | i
|                  |   |     X             | e
|                  |   |     X             |
| O  X  X  X  X  X |   |     X             |
| O  X  X  X  X  X |   |     X        X    |
+-1--2--3--4--5--6--------7--8--9-10-11-12-+
Pipcount  X:  83  O: 102  X-O: 0-0/Money (1)
CubeValue:  1

Let's say X rolls 5-5 for all remaining rolls. O rolls 6-4 followed by
66 for all remaining rolls.

If X plays badly by playing 8/6 8/5 he will loose the game and his
luck rate is -142. If X plays 11/6 correctly he will win the game
(barely) with a luck rate of 3.

Same rolls, one checker play error. Still the luck rate is negative just
because of one "tiny" misplay.

Eskimo
```

 Douglas Zare  writes: ```> How much does luck and skill correlate? They certainly aren't mutually exclusive. The luck in backgammon means that the game isn't decided by who makes the first mistake. The luck means that it matters how much better than your opponent you play, not just whether you play better. The flip side of the coin is that you can determine how much better one player is than another by determining how much luck is needed for each to win. This works if you measure luck in mwc in an unbiased fashion, not in EMG or EMG/move. > When two players are comparable in skill a -5 or -10 in luck rate > (Snowie terms) pretty much decides who wins. That might be reasonable for money play, if you play for a fixed amount of time. In match play, you don't stop after a set period of time, but after one side is ahead by 50% mwc. If luck is properly measured, then between competent players, the luckier would win the match over 99% of the time. The main reason you can find examples that don't look like this is that Snowie's luck rate is a bad measure. A luck rate in EMG mainly tells how the match was won, i.e., what match scores were hit, as well as how easy the takes were for any doubles accepted. Suppose in a 3 point match player A wins 1 point, then another single game. Then player B wins the Crawford game, doubles player A in, and wins at DMP. Who was luckier? Player B, obviously, unless A was playing absolutely terribly. Player B won. Who had more luck in terms of EMG? Perhaps player A, by about 0.200, and if the match took 200 moves the luck rate for player A might be +1 millipoint per move. That's because with perfect play, the luck in EMG for player A was +1 in the first game, about +1.2 in the second game, -1 in the third game, and -1 in the fourth. When expressed in mwc, the luck for player B should be about +50%. It is 50%+net skill. So, if player A made one little mistake and player B played perfectly, the total luck for B was +49% mwc. If player A makes the same mistake and then wins, the total luck for player A was +51% mwc. Even though the luckier player wins, the weaker player needs more luck to win, hence wins less often, since luck averages to 0. > Same rolls, one checker play error. Still the luck rate is negative > just because of one "tiny" misplay. The luck for a roll is independent of how you play it. However, there is no reason to expect the luck of a particular subsequent roll or sequence (which you specified) to be the same, no matter how you play this one. If you win the opening roll, 2-1, splitting is about the same as slotting. If I respond 4-3, this is a lucky roll for me if you have slotted, since I get to hit. It is an unlucky roll for me if you have split. Of course, to balance this, there are rolls which are luckier if you have split than if you have slotted, such as 5-5. I don't see any reasonable measure of luck that says, a priori, what the luck was of the sequence 2-1, 4-3. > I have a hard time figuring out if my play is improving or not just > because my luck rate has been "awful" for so long. It might well be > that my play has improved a lot, but because I was having a bad run > I don't see as much gain as I should have. This is a bit of a > motivation issue. Why focus on the results or your luck rate? Much more useful is to consider your error rate or your net skill advantage. It makes more sense to ask whether you play as well when your luck so far in a match has been bad as you do when your luck has been good. Douglas Zare ```

### Luck versus Skill

Are good players just luckier?  (Douglas Zare, Sept 2000)
Are luck and skill related?  (Eskimo+, Feb 2003)
Does backgammon need less luck?  (Raccoon, Jan 2008)
How much of backgammon is luck?  (Wai Mun Yoon, Jan 1998)
How much skill versus luck?  (Alexandre Sierra, Nov 2000)
How much skill versus luck?  (JP White+, Aug 2000)
How often to win with perfect play?  (Robert-Jan Veldhuizen, Nov 2000)
Is backgammon gambling?  (Luc Palmans+, Oct 2010)
Is backgammon gambling?  (Kevin D. McLeaster, Sept 1997)
Is there really luck in backgammon?  (benf+, Jan 2012)
Recognizing luck  (Walter Trice, Dec 2004)
Strange result  (az-willie+, Mar 2003)
The Bower Luck-O-Meter  (Gary Wong, Aug 1998)
Why are stronger players luckier?  (Bob Sweeney+, Oct 2002)