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

    (www.researchgate.net)
    392 points seanhunter | 28 comments | 19 Nov 24 09:03 UTC | HN request time: 1.424s | source | bottom
    1. acyou ◴[19 Nov 24 17:23 UTC] No.42185920[source]▶
    The paper looks like it has a large sample size, but it actually has a sample size of only 48 testers/flippers. Some of the videos of those testers show very low, low-rpm coin tosses, we're talking only 1-2 flips. Where they also flipped thousands of times, presumably in the same way. So there is actually a very small sample size in the study (N = 48), where testers that don't flip properly (low rpm, low height, few coin rotations) can affect the results disproportionately.

    Doesn't look like the study author backgrounds are particularly focused on statistics. I would presume with 48 authors (all but 3 of which flipped coins for the study), the role of some might have been more test subject than author. And isn't being the subject in your own study going to introduce some bias? Surely if you're trying to prove to yourself that the coins land on one side or another given some factor, you will learn the technique to do it, especially if you are doing a low-rpm, low flip. Based on the study results, some of the flippers appear to have learned this quite well.

    If the flippers (authors) had been convinced of the opposite (fair coins tend to land on the opposite side from which they started) and done the same study, I bet they could have collected data and written a paper with the results proving that outcome.

    replies(10): >>42186149 #>>42186157 #>>42186224 #>>42186287 #>>42186401 #>>42186585 #>>42186595 #>>42187589 #>>42187685 #>>42187932 #
    2. salt4034 ◴[19 Nov 24 17:43 UTC] No.42186149[source]▶
    > testers that don't flip properly

    I think that's the point. It shows that people don't usually flip properly, leading to biased results.

    replies(3): >>42186225 #>>42186573 #>>42186611 #
    3. saalweachter ◴[19 Nov 24 17:43 UTC] No.42186157[source]▶
    If you are doing anything with human subjects, even something dumb like having them flip coins for an hour while recording the results, you need approval from your local ethics board.

    If you are doing self-experimentation, you do not.

    48 "authors" is a bit extreme, but it's the norm to do some light human research with a half dozen authors as the subjects.

    4. KwisatzHaderack ◴[19 Nov 24 17:49 UTC] No.42186224[source]▶
    > only 48 testers/flippers

    I assumed they did these coin flips were done using a machine. But I guess they wanted to test if human flippers because they wanted to make claims about the human coin flip phenomenon.

    replies(2): >>42186415 #>>42187418 #
    5. fluoridation ◴[19 Nov 24 17:49 UTC] No.42186225[source]▶
    But is that the case? The only way I've ever seen people flip a coin is by flicking it in the air with their thumb and either catching it or letting it hit a surface. I've never seen someone flip a coin like it was a die.
    6. binarymax ◴[19 Nov 24 17:54 UTC] No.42186287[source]▶
    1-2 flips should just invalidate the toss. Anyone in a real scenario upon seeing this would call shenanigans.

    We need some minimum flippage for the toss to count.

    7. its-summertime ◴[19 Nov 24 18:05 UTC] No.42186401[source]▶
    > the role of some might have been more test subject than author

    The reason is because it was used as incentive:

    > Intrigued? Join us and earn a co-authorship

    Per the linked youtube video.

    8. kybernetikos ◴[19 Nov 24 18:06 UTC] No.42186415[source]▶
    But if you get someone to flip a coin thousands of times for a boring reason, I would lose confidence that they are flipping in the same way a normal human would.
    9. lcnPylGDnU4H9OF ◴[19 Nov 24 18:22 UTC] No.42186573[source]▶
    There is a [video presentation of the paper](https://www.youtube.com/watch?v=-QjgvbvFoQA) which does a good job of explaining the inspiration for the study within the first few minutes.

    It sounds like what they were intending to study is the actual variance that is introduced, on average, by imperfections in throws conducted by humans. Unless that's mistaken, it's a fair point to consider the n=48 here. Did they discover an average that can be generalized to humans or just to those 48?

    replies(1): >>42186614 #
    10. tomrod ◴[19 Nov 24 18:23 UTC] No.42186585[source]▶
    Actually, I think it's more sound to approach this with clustered standard errors. Basic intuition is similar, but the sample size is what it is per person, and your observations aren't independent across draws but are across people.

    https://en.m.wikipedia.org/wiki/Clustered_standard_errors

    11. bambax ◴[19 Nov 24 18:24 UTC] No.42186595[source]▶
    The real lesson is probably that if you're skilled enough, and/or train for long enough, you can influence the odds significantly without anyone ever noticing anything.
    replies(1): >>42193546 #
    12. arandomusername ◴[19 Nov 24 18:26 UTC] No.42186611[source]▶
    Except that flipping a coin hundreds/thousands of time in a row is not a representive of how people will flip a coin a single time/few times.
    13. chongli ◴[19 Nov 24 18:26 UTC] No.42186614{3}[source]▶
    Yes and what immediately jumps out to me as a source of bias is that they asked this small group of 48 coin flippers to flip thousands of times each. I would’ve thought it would be obvious that when you ask people to do something thousands of times they might do it in a different (and biased) way than someone doing that thing only once.

    Get a hundred thousand people to flip a coin once each and then see what happens!

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    14. fluoridation ◴[19 Nov 24 19:08 UTC] No.42186986{4}[source]▶
    What's more, from the numbers cited it sounds like they had 48 people do nothing but flip coins for 8 hours (avg. 15 flips/min). Whether continuous or with breaks, there's no way you won't become seriously consistent. 7000 flips is many more flips most people will perform in their entire lives.
    replies(1): >>42187453 #
    15. dfxm12 ◴[19 Nov 24 19:53 UTC] No.42187402{4}[source]▶
    Get a hundred thousand people to flip a coin once each and then see what happens!

    Of all the stats we collect in sports, I wonder if someone has info on coin tosses in sports like American Football, Tennis, etc. I wonder if there are even rules regulating how a coin should be tossed in different sports...

    replies(1): >>42193559 #
    16. halgir ◴[19 Nov 24 19:55 UTC] No.42187418[source]▶
    If you programmed a machine to flip a coin in the same exact way every time, would you not expect the coin to land the same way every single time? If you program some randomness into the machine to simulate human flipping, then you'd simply move scrutiny from the coin to the machine's programming.

    I think the result could be better described as "humans tend to flip fair coins to land on the side they started".

    replies(1): >>42189700 #
    17. dylan604 ◴[19 Nov 24 19:58 UTC] No.42187453{5}[source]▶
    In some circles, they'd make a post about how their "AI" flipped a coin 8000 times.

    Waiting for the HNer that likes electronics hacking to Show HN: My coin flipping robot I built over a weekend for consistent flips.

    18. anigbrowl ◴[19 Nov 24 20:11 UTC] No.42187589[source]▶
    testers that don't flip properly

    Clearly the coin flips at the beginning of sports fixtures need to be assessed by a panel of highly skilled judges who can pronounce on their validity. We'll also need local, regional, national, and international organizations to train, select, and maintain the quality of coin flipping judges and to maintain the integrity of the discipline while moving forward as new coins are minted and different sorts of flipping styles are proposed by. Membership of such organizations should be limited to those afilliated with the Ancient Order of Coin Flippers.

    replies(1): >>42187733 #
    19. jdlshore ◴[19 Nov 24 20:22 UTC] No.42187685[source]▶
    The paper is an experimental validation of a previous paper that presented a statistical model. The experiment found the exact results predicted by the model. The reason for the non 50/50 result is precession of the coin.
    20. askvictor ◴[19 Nov 24 20:26 UTC] No.42187733[source]▶
    I was more thinking we'll need a Department of Randomness (or Ministry of Randomness for Westminster countries)
    replies(1): >>42187968 #
    21. ◴[19 Nov 24 20:48 UTC] No.42187932[source]▶
    22. pc86 ◴[19 Nov 24 20:52 UTC] No.42187968{3}[source]▶
    Perhaps whether it's a Department or a Ministry could be decided randomly.
    replies(1): >>42188396 #
    23. Green-Man ◴[19 Nov 24 21:41 UTC] No.42188396{4}[source]▶
    Randomly how? By a coin toss? Who will toss then? How many times? How skilled the participants should be? All these important questions must be decided by some authority. Sort of a Department of Equal Distribution. Or a Ministry of Fair Tosses. Wait a second...
    replies(1): >>42191337 #
    24. saagarjha ◴[20 Nov 24 00:46 UTC] No.42189700{3}[source]▶
    One would expect chaos effects to come into play.
    replies(1): >>42191282 #
    25. oefnak ◴[20 Nov 24 06:28 UTC] No.42191282{4}[source]▶
    One might, but that would be wrong.
    26. moi2388 ◴[20 Nov 24 06:44 UTC] No.42191337{5}[source]▶
    The obvious solution is to hand it off to the Department of Catch 22. Or the Ministry of infinite recursion. Wait..
    27. lupire ◴[20 Nov 24 12:59 UTC] No.42193546[source]▶
    That has been known for decades. It's not the lesson of this paper.
    28. skykooler ◴[20 Nov 24 13:00 UTC] No.42193559{5}[source]▶
    Having stats on the outcome of coin tosses in sports wouldn't help, because it's unlikely that the state of the coin before flipping was recorded.