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Fair coins tend to land on the side they started (2023)

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31–40 of 193 posts

Re: Fair coins tend to land on the side they started (2023)

#31

Easy way to get a fair result from an unfair coin toss: Flip the coin twice in a row, in this case starting with the same side facing up both times, so it's equally unfair for both tosses. If you get heads-heads or tails-tails, discard and start over until you get either heads-tails or tails-heads, which have equal probabilities (so you can say something like HT = "heads" and TH = "tails"). This works even if the coi…

I’ve seen this attributed to John von Neumann, of all people

Re: Fair coins tend to land on the side they started (2023)

#32
post #26
post #18

Earlier quoted context omitted.

That's not the problem. You can test that by using a highly secure random number generator, e.g. /dev/random in Linux, to select the initial side. Keep track of that initial side, record the side it lands on. This paper shows a same-side bias, not a heads bias.

A same side bias is either a heads bias or a tails bias.

Its not, its a bias towards which side the coin started on.

Re: Fair coins tend to land on the side they started (2023)

#33
post #24

I wouldn't be surprised if there is something to it, but I suspected they didn't use legitimate coin flips (because it seems like a large amount of people can't really flip a coin), and looking at the videos confirms it, at least for the flips done by Bartos: https://osf.io/6a5hy/ They're very low RPM and very low time in the air. Nothing I would accept for any decision worth flipping a coin for.

That's not tossing a coin, that's barely throwing it in the air.

To me this kills the credibility of the entire study and of the authors.

Sure, there may be something to it, but people will have a very different thing on their mind unless they check the video, which I wouldn't have done without your prompting.

It's unlikely they don't understand how misleading it is.

And somehow I have the intuition a proper coin toss will not exhibit the same properties.

Re: Fair coins tend to land on the side they started (2023)

#34

Easy way to get a fair result from an unfair coin toss: Flip the coin twice in a row, in this case starting with the same side facing up both times, so it's equally unfair for both tosses. If you get heads-heads or tails-tails, discard and start over until you get either heads-tails or tails-heads, which have equal probabilities (so you can say something like HT = "heads" and TH = "tails"). This works even if the coi…

What if consecutive unfair coin flips are not independent?

Re: Fair coins tend to land on the side they started (2023)

#35

Easy way to get a fair result from an unfair coin toss: Flip the coin twice in a row, in this case starting with the same side facing up both times, so it's equally unfair for both tosses. If you get heads-heads or tails-tails, discard and start over until you get either heads-tails or tails-heads, which have equal probabilities (so you can say something like HT = "heads" and TH = "tails"). This works even if the coi…

If anyone wants to look up why this might work, it's a Whitening transform [0]. I can't find the name of the algorithm itself being describe in the parent but there's more than just that for accomplishing the same thing.

0: https://en.wikipedia.org/wiki/Whitening_transformation

Re: Fair coins tend to land on the side they started (2023)

#37
post #26
post #18

Earlier quoted context omitted.

That's not the problem. You can test that by using a highly secure random number generator, e.g. /dev/random in Linux, to select the initial side. Keep track of that initial side, record the side it lands on. This paper shows a same-side bias, not a heads bias.

A same side bias is either a heads bias or a tails bias.

How? I described how to randomize the initial side. Boolean true for heads, boolean false for tails, for example. Keep pulling those from the Kernel's secure RNG.

Re: Fair coins tend to land on the side they started (2023)

#38
post #28
post #14

Earlier quoted context omitted.

How good are you at Bayesian statistics, conditionalization, and understanding various biases? The simulation here should be good (it's better than mine).

Next you'll cite Bible verse.

I don't think Bible verses are related.

There are multiple ways to ground Bayesian statistics without resorting to grounding in coin flips. The simplest one isn't that robust, there's a mathematical one but it's abstract and uses calculus, there's a quantum one but I'm not even going there, and there's a highly robust one that's too complex for me to understand.

Re: Fair coins tend to land on the side they started (2023)

#39

Flip it twice. Once to determine which side is up at second throw. Reverse to counter bias at start of second throw. Then flip again for final result.

That only works for a fixed bias, it's gameable if the person tossing the coin controls the bias.

That is outside the preconditions of the paper: „if the person tossing the coin controls the bias“

Re: Fair coins tend to land on the side they started (2023)

#40
post #24

I wouldn't be surprised if there is something to it, but I suspected they didn't use legitimate coin flips (because it seems like a large amount of people can't really flip a coin), and looking at the videos confirms it, at least for the flips done by Bartos: https://osf.io/6a5hy/ They're very low RPM and very low time in the air. Nothing I would accept for any decision worth flipping a coin for.

This was my first objection as well. However, if most people flip coins like that, then the measurements are valid -- the conclusions are about what average people will do, not a perfect mechanical coin flip. Otherwise you're falling in the no true coin flip fallacy.
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