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

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

#141

Post by fbartos »

Hi, I'm the first author of the manuscript, so I thought I could answer some of the questions and clarify some issues (all details are in the manuscript, but who has the time to read it ;)

Low RPM tosses: Most of the recordings are on crapy webcams with ~ 30FPS. The coin spin usually much faster than the sensor can record which results in often non-spinning-looking flips. Why did we take the videos in the first place? To check that everyone collected the data and to audit the results.

Building a flipping matching: The study is concerned with human coin flips. Diaconis, Holmes, and Montgomery's (DHM, 2007) paper theorize that the imperfection of human flips causes the same-side bias. Building a machine completely defeats the purpose of the experiment.

Many authors and wasted public funding: We did the experiment in our free time and we had no funding for the study = no money was wasted. Also, I don't understand why are so many people angry that students who contributed their free time and spent the whole day flipping coins with us were rewarded with co-authorship. The experiment would be impossible to do without them.

Improper tosses: Not everyone flips coin perfectly and some people are much worse at flipping than others. We instructed everyone to flip the coin as if they were to settle a bet and that the coin has to flip at least once (at least one flip would create bias for the opposite side). We find that for most people, the bias decreased over time which suggests that people might get better at flipping by practice = decrease the bias and it also discredits the theory that they learned how to be biased on purpose. From my own experience - I flipped coins more than 20,000 times and I have no clue how to bias it. Also, we did a couple of sensitivity analyses excluding outliers - the effect decreased a bit but we still found plentiful evidence for DHM.

If you doubt my stats background, you are more than welcome to re-analyze the data on your own. They are available on OSF: https://osf.io/mhvp7/ (including cleaning scripts etc).

Frantisek Bartos

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

#142

Post by [deleted] »

acyou wrote: post #96

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…

[deleted]

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

#143

Post by pc86 »

askvictor wrote: post #140
anigbrowl wrote: post #136

Earlier quoted context omitted.

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…

I was more thinking we'll need a Department of Randomness (or Ministry of Randomness for Westminster countries)

Perhaps whether it's a Department or a Ministry could be decided randomly.

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

#144

Post by mihaic »

Here's a little through experiment I use to come to this conclusion:

Let's say you start a counter from the number 0, and keep on incrementing it. The moment you stop it to look at the counter, is it going to be odd or even?

At any given moment in time, either the number of observed odd numbers is the same as the number of even numbers, or the number of even numbers is larger by 1 (such as going from 0 to 1 to 2). So in the end there's always a slightly larger chance at stopping on an even number.

I know it's more complicated, I use it just as an intuitive explanation.

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

#145

Post by ineptech »

fbartos wrote: post #141

Hi, I'm the first author of the manuscript, so I thought I could answer some of the questions and clarify some issues (all details are in the manuscript, but who has the time to read it ;) Low RPM tosses: Most of the recordings are on crapy webcams with ~ 30FPS. The coin spin usually much faster than the sensor can record which results in often non-spinning-looking flips. Why did we take the videos in the first place…

Hi, thanks for replying. I have no complaints about your analysis, and agree that your results strongly support the D-H-M model (that there is a slight bias in coin-flipping over all and that it is caused by precession). However, it looks like about a third of your volunteers had little or no bias, presumably due to flipping end-over-end with no precession, and about a third had a lot of precession and a lot of bias.

Your paper draws the conclusion that coin-flipping inherently has a small-but-significant bias, but looking at table 2 it seems like an equally valid conclusion would be that some people flip a coin with no bias and others don't. Did you investigate this at all? In particular, I'd expect that if you took the biggest outliers, explained what precession is and asked them to intentionally minimize it, that the bias would shrink or disappear.

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

#146

Post by emmelaich »

fbartos wrote: post #141

Hi, I'm the first author of the manuscript, so I thought I could answer some of the questions and clarify some issues (all details are in the manuscript, but who has the time to read it ;) Low RPM tosses: Most of the recordings are on crapy webcams with ~ 30FPS. The coin spin usually much faster than the sensor can record which results in often non-spinning-looking flips. Why did we take the videos in the first place…

The first thing I looked for was how high was the flip and did it land on a hard or soft surface. Neither seemed to be mentioned in the paper.

From the one video I looked at, the flip seems to be a few feet high at most, and land back in the hand.

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

#147

Post by boomboomsubban »

anigbrowl wrote: post #139
damidekronik wrote: post #19

Earlier quoted context omitted.

From this year's Iq: Botany: Jacob White and Felipe Yamashita, for finding that certain plants imitate the leaf shape of nearby plastic plants and concluding that "plant vision" is plausible. This somehow doesn't fit the Iq award in my mind.

They 'need' to fill slots not that the IN awards have become an annual media event (presumably yielding some profit) so they've taken to mocking perfectly legitimate research as long as it is in some way scatalogical or counterintuitive. I lost interest in the Ig Nobel prize as a result; they've gone from an intermittent amusement to a celebration of ignorance. Incidentally the plant mimicry thing seems to be a defen…

The Ig Nobel has always been for serious science that sounds silly. Their website begins with

>The Ig Nobel Prizes honor achievements so surprising that they make people LAUGH, then THINK. The prizes are intended to celebrate the unusual, honor the imaginative — and spur people’s interest in science, medicine, and technology.

There goal has never been to mock the award winners.

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

#148

Post by fbartos »

emmelaich wrote: post #146
fbartos wrote: post #141

Hi, I'm the first author of the manuscript, so I thought I could answer some of the questions and clarify some issues (all details are in the manuscript, but who has the time to read it ;) Low RPM tosses: Most of the recordings are on crapy webcams with ~ 30FPS. The coin spin usually much faster than the sensor can record which results in often non-spinning-looking flips. Why did we take the videos in the first place…

The first thing I looked for was how high was the flip and did it land on a hard or soft surface. Neither seemed to be mentioned in the paper. From the one video I looked at, the flip seems to be a few feet high at most, and land back in the hand.

> In each sequence, people randomly (or according to an algorithm) selected a starting position (heads-up or tails-up) of the first coin flip, flipped the coin, caught it in their hand, recorded the landing position of the coin (heads-up or tails-up), and proceeded with flipping the coin starting from the same side it landed in the previous trial (we decided for this “autocorrelated” procedure as it simplified recording of the outcomes). (p.3)

Wrt to the height, that naturaly varied among people and flips and we did not measure it.

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

#149

Post by fbartos »

ineptech wrote: post #145
fbartos wrote: post #141

Hi, I'm the first author of the manuscript, so I thought I could answer some of the questions and clarify some issues (all details are in the manuscript, but who has the time to read it ;) Low RPM tosses: Most of the recordings are on crapy webcams with ~ 30FPS. The coin spin usually much faster than the sensor can record which results in often non-spinning-looking flips. Why did we take the videos in the first place…

Hi, thanks for replying. I have no complaints about your analysis, and agree that your results strongly support the D-H-M model (that there is a slight bias in coin-flipping over all and that it is caused by precession). However, it looks like about a third of your volunteers had little or no bias, presumably due to flipping end-over-end with no precession, and about a third had a lot of precession and a lot of bias.…

Yes, there is indeed a lot of heterogeneity in the bias between flippers and we are going to put more emphasis on it in an upcoming revision. However, it's hard to tell whether there are two groups or a continuous scale of increasing bias. From our examination of the data, and continuum seem to be the more likely case, but we would need many many more people flipping a lot of coins to test this properly.

Yes, training the most wobbly flippers sounds like a very interesting idea. It might indeed answer additional questions but it's not really something I wanna run more studies on :)

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

#150

Post by Green-Man »

pc86 wrote: post #143
askvictor wrote: post #140

Earlier quoted context omitted.

I was more thinking we'll need a Department of Randomness (or Ministry of Randomness for Westminster countries)

Perhaps whether it's a Department or a Ministry could be decided randomly.

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...
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