not the friendliest game?

[veggivet]

Here's a game with 12 doubles. Table # 261616166

I know enough about statistics to realize that the algo throws doubles WAY too frequently, assuming the dice are not 'rigged'.

[veggivet]

And my very next game had 7 doubles...I'm not cherry picking here. This is an inherent design flaw in the algo.

[dschingis27]

Here's a game with 12 doubles. Table # 261616166

I know enough about statistics to realize that the algo throws doubles WAY too frequently, assuming the dice are not 'rigged'.

In the game you linked, your opponent only had 7 doubles. I would be interested in the one with 12, maybe you can edit the ID.
And sorry, you point to single games as evidence for sth and you claim you know statistics? That's not how statistics works.

[veggivet]

First game played today: 10 doubles in 30 moves. Please calculate the odds of essentially doubling the expected 16.7% frequency of throwing any double given a pair of fair dice. Table #2611705031 if you want to take a look. I realize that statistics is all about larger numbers, but having played nearly 1000 games, my sense is that doubles occur much more frequently than they would if the dice were truly random. If you experience a 1 in 500 year flood every 5-10 years, it's probably time to rethink the '1 in 500' terminology.

[RicardoRix]

I looked at the code for backagammon. and was planning on doing some dice rolling simulations.
But the original developer has already done the work by recording all the rolls and double in the statistics.

Here are the statistics from all the games ever played on BGA:
https://boardgamearena.com/playerstat?i ... 98&game=53

Code: Select all

veggivet average	All players' average	Winners' average
Dice rolls	25.53	25.93	26.18
Double rolls	4.17	4.22	4.46

Notice how the 'doubles' * 6 = 'dice rolls'

-------------------

It's also notable that backgammon uses the bga_rand() function for rolling the dice.

Code: Select all

    private function rollDice($forbidDouble = false)
    {
        self::incStat( 1, "turns_number");

        // Roll dices
        $dice1_value = bga_rand(1, 6);
        $dice2_value = bga_rand(1, 6);

I previously did rigorous 5000 random number simulation with bga_rand() on BGA Studio, you can see the results here:
https://boardgamearena.com/forum/viewto ... and#p59122

[Jellby]

The odds are the same as of getting at least 10 sixes in 30 dice, which is about 2%, so you can expect it to happen about once every 50 games. But you should not be surprised if it happens twice in 10 games, or never in 100 games.

[Silene]

I realize that statistics is all about larger numbers, but having played nearly 1000 games, my sense is that doubles occur much more frequently than they would if the dice were truly random. If you experience a 1 in 500 year flood every 5-10 years, it's probably time to rethink the '1 in 500' terminology.

Your stats show that it actually is very close to 1/6 for you.

So you can either explain the mismatch of your perception and your stats with manupilated statistics or it is probably time to rethink your ability to perceive random events unbiased.

[Romain672]

First game played today: 10 doubles in 30 moves. Please calculate the odds of essentially doubling the expected 16.7% frequency of throwing any double given a pair of fair dice. Table #2611705031 if you want to take a look. I realize that statistics is all about larger numbers, but having played nearly 1000 games, my sense is that doubles occur much more frequently than they would if the dice were truly random. If you experience a 1 in 500 year flood every 5-10 years, it's probably time to rethink the '1 in 500' terminology.

It was game https://boardgamearena.com/gamereview?table=261705031 you added a 1 by mistake.
The probability is 1/50.7 to have 10 doubles or less.
Here is the number of each roll not double between every double of the game, it started and ended by a non double:
32001161014
Which mean we got 19 non doubles & 10 doubles. Which increase the probability to 1/65.

Which is totally what you expect. You did 5 games between your previous post and this one, which mean we can divide that probability by 5 (to be simple), which give 1/13.
It stay unlikely, but nothing weird to see there.

[The_Trioker]

To get back to the original topic proposed by SebiCools , I totally agree that there are far too many players complaining about their bad luck in the chat. If someone have an issue with the randomness of the dice, I don't think that he should put the blame on his opponent.

The fact is that this game is played with dice, and that the luck factor is greatly increased by the absence of the doubling cube. The one and only parameter your opponent have to deal with is how he moves his men. If he does this in a skillfull fashion, I congratulate him for doing that. If he does not, then I'm happy to have greater chances to win!

In either case I cannot see any good reason for whining about bad dice. I've watched plenty of games from the #1 player in the world Mochy Masayuki, and never ever saw him complaining about bad luck. Actually, I never ever saw any of the "giants of backgammon" behave in such a way.

[Paddles]

First game played today: 10 doubles in 30 moves. Please calculate the odds of essentially doubling the expected 16.7% frequency of throwing any double given a pair of fair dice. Table #2611705031 if you want to take a look. I realize that statistics is all about larger numbers, but having played nearly 1000 games, my sense is that doubles occur much more frequently than they would if the dice were truly random. If you experience a 1 in 500 year flood every 5-10 years, it's probably time to rethink the '1 in 500' terminology.

Your own analogy is the problem here - what you are describing is not even remotely like a "1 in 500 year flood". The probability of getting exactly 10 doubles in 30 moves is about 1.3%. As someone else posted earlier, the probability of getting 10 or more doubles in 30 rolls is higher than that - around 1.97%. If you played one game of Backgammon every day with fair/unbiased dice, you would expect to see it happening around 7 times a year. Your (incorrect) sense about how rare such an event is is leading you to draw the wrong conclusions about the random number generator. You'd have to be getting up to around 17 or 18 rolls out of 30 being doubles to get to the level of a "1 in 500 year event" (and even then, 1 in 500 years is rare, not impossible).

Not long ago, I lost a game that I was ahead on because the other player rolled 6-6, 6-6, 5-5 in a row, which was the minimum combination that would have let them win from that position. The probability of any one specific game finishing like that is low - but it's not "1 in 500 years" low, I've played enough backgammon in my life that the probability of that happening to me some time is likely somewhere around 10-20%. It would only have been suspicious if my opponent had predicted it beforehand. No point complaining about it, they didn't cheat, rare events are just that - rare, not impossible. I'm sure there have been times where I've unexpectedly won from behind with a lucky combination of rolls too.

I'd be far more suspicious if the BGA (or any other site's) random number generator never produced these sort of results, because that would suggest that they were manipulating the results to pander to certain peoples' misconceptions about probability and hence avoid complaints about the random number generator.