2. ## Re: Bias in heads-or-tails

Interesting article!

Reminds me too much of my statistics class in school -- in a bin of red/blue/yellow balls... odds of getting red ball... {shudder}

[img]images/icons/tongue.gif[/img]

3. ## Re: Bias in heads-or-tails

What if you randomly determine which face the coin is going to start on?

Does that make it fair?

4. ## Re: Bias in heads-or-tails

Originally posted by PedroG:
What if you randomly determine which face the coin is going to start on?

Does that make it fair?
<font size="2" face="Verdana, Arial, Helvetica">..well according to the article no ..

This slight bias pales when compared with that of spinning a coin on its edge. A spinning penny will land as tails about 80 percent of the time, Diaconis says, because the extra material on the head side shifts the center of mass slightly.
<font size="2" face="Verdana, Arial, Helvetica">Cheers!
Aatish

5. ## Re: Bias in heads-or-tails

Originally posted by PedroG:
What if you randomly determine which face the coin is going to start on?

Does that make it fair?
<font size="2" face="Verdana, Arial, Helvetica">As long as you do not use a coin toss to determine which face to start on. [img]images/icons/smile.gif[/img]

6. ## Re: Bias in heads-or-tails

Aatish,

I believe they were referring to placing the coin on a table and then spinning it. Not with flipping the coin.

Charles,

What if I roll a die? Surely those aren't at all biased?

7. ## Re: Bias in heads-or-tails

Originally posted by PedroG:
Charles,

What if I roll a die? Surely those aren't at all biased?
<font size="2" face="Verdana, Arial, Helvetica">As long as the die is perfectly square, all the weight is evenly distributed, and there is no difference in the surface and frictional coefficient of each face, and the die is required to be tossed/rolled in such a way that it bounces off of irregular surfaces thus defeating any attempt to spin the die or otherwise control how it lands. (Note how in a casino you have to throw the craps dice off the wall around the table, that wall having a bumpy surface making it essentially humanly impossible to control how the dice bounce off of it&mdash;unless you use loaded dice [see above]).

8. ## Re: Bias in heads-or-tails

Well, if coins are out, and dice are out, what's left?

Perhaps, instead of flipping a coin, the opposing sides should just play paper-scissors-rock (best two out of three.)

I wonder if pro sports teams could file a lawsuit, since the coin toss isn't completely fair. The last Superbowl could have had a different outcome, if it weren't for that stupid cointoss... [img]images/icons/smile.gif[/img]

9. ## Re: Bias in heads-or-tails

Pedro, I wonder if the extra weight on the head side has any effect on flipping too. :-?

But there could be many alternatives [img]images/icons/grin.gif[/img] - maybe throwing a handfull of coins (say a large odd number) and then matching the result?
or maybe using a program for random number generation - and see if the result is odd or even?

Cheers!
Aatish

10. ## Re: Bias in heads-or-tails

Well, Aatish, using a program might work, but has there been a study on just how fair that would be? Computers can't create truely random numbers (at least not on their own) so I wonder if there would be a bias towards any set of numbers.

I do like the handfull of coins, but the added risk of injury from extra projectiles could result in more lawsuits [img]images/icons/smile.gif[/img] And I could just see a group of people diving for the money before it even hit the ground...

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