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Mathematician says coin flips aren't 50/50

Dr. D : 1/25/2022 2:36 pm
With all this talk about the coin flip, I searched a little to see if the odds really are 50/50.

From the lonked article, mathematician Persi Diaconis, who has studied coin flips says:

"The coin toss is not about probability at all. It is about physics, the coin, and how the “tosser” is actually throwing it. The majority of times, if a coin is heads-up when it is flipped, it will remain heads-up when it lands. Diaconis has even trained himself to flip a coin and make it come up heads 10 out of 10 times.

He said "Super Bowl coins are much larger (than normal coins, I don't know about playoff coins). And the effect is probably much bigger,” Diaconis said.

His advice? “Try to catch a glimpse of how it starts out. Is it heads-up when it’s flipped? Then bet on it coming up on that same side."

Tails does fail.


not 50/50 - ( New Window )
Fascinating...  
Festina Lente : 1/25/2022 2:40 pm : link
I always had a feeling it might not be competitive 50/50 because of the asymmetry of the faces onthe coins.
I wonder if the players see the way the coin is lying on the refs hand beige they can. If this information is available then they should make an effort to conceal the call until the call has been made.
This is pretty interesting.  
81_Great_Dane : 1/25/2022 2:41 pm : link
Coin flips at the start of games, and more importantly of overtime, assume that the outcome is random. Maybe not. So: What now?

At the very least, it seems that the coin should be hidden from whoever going to call it.
I want to see this idiot  
BlackLight : 1/25/2022 2:42 pm : link
flip a coin and have it come up heads ten times out of ten on purpose.
I you may be interested to hear that another theoretically 50/50  
Festina Lente : 1/25/2022 2:43 pm : link
Occurrence that turns out to not be is the sex of a baby. Apparently, there is a slightly higher chance that the embryo will remain female than become male although im not sure of the actual statistic. I can guess the reason but i have never confirmed it.
This story makes if very clear...  
BamaBlue : 1/25/2022 2:44 pm : link
Mathematician's have WAY too much time on their hands.
This guy...  
Chris in Philly : 1/25/2022 2:47 pm : link
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!
RE: This guy...  
mfsd : 1/25/2022 2:49 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


LOL
Chris  
gidiefor : Mod : 1/25/2022 2:51 pm : link
you slay me LoL
The big difference is that he talks about the coin being caught  
JohnB : 1/25/2022 2:52 pm : link
NFL refs don't catch the coin. It bounces on turf, or grass or whatever surface is on the field. All of them different. All of them effect the outcome differently.

It's a 50/50 chance.
RE: The big difference is that he talks about the coin being caught  
Section331 : 1/25/2022 2:57 pm : link
In comment 15574375 JohnB said:
Quote:
NFL refs don't catch the coin. It bounces on turf, or grass or whatever surface is on the field. All of them different. All of them effect the outcome differently.

It's a 50/50 chance.


They used to catch it, before that infamous botched coin toss call with (IIRC?) PITT, but yeah, that's a pretty big miss for Dr Big Brain.
RE: I want to see this idiot  
Dr. D : 1/25/2022 3:02 pm : link
In comment 15574351 BlackLight said:
Quote:
flip a coin and have it come up heads ten times out of ten on purpose.

"this idiot" has a PhD in statistics from Harvard and is a professor at Stanford.
CIP beat me to it  
Dr. D : 1/25/2022 3:04 pm : link
re "this idiot"
You know what?  
AGK_GiantsFan : 1/25/2022 3:15 pm : link
WHO CARES!!!!!
RE: I want to see this idiot  
k2tampa : 1/25/2022 3:25 pm : link
In comment 15574351 BlackLight said:
Quote:
flip a coin and have it come up heads ten times out of ten on purpose.


And do it in front of 60,000 screaming fans in the cold and wind and possibly rain or snow.
Not to mention the ref's physical situation can be affected by the weather. Each coin might have different characteristics. Also, the coin goes to the ground, so there are factors of physics that will affect whether there is a bounce, and the dynamics of the bounce. The height of the tosser's hand will have an impact, along with the force used to toss it. The coin would also need to have the same exact placement and balance on the thumb for each toss. Guy is looking for his 15 minutes of fame.

I have no doubt you could program a robot to do that in pristine conditions, but not a random person, especially one who isn't trying to make that happen.
RE: This guy...  
markky : 1/25/2022 3:32 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


He never won the Fields medal. Who's the idiot now?
Well, can someone use google  
ZogZerg : 1/25/2022 3:40 pm : link
to get the status for playoff coin flips?
coin toss  
drac56 : 1/25/2022 3:43 pm : link
Some people have too much time on their hands
RE: RE: I want to see this idiot  
BlackLight : 1/25/2022 3:44 pm : link
In comment 15574395 Dr. D said:
Quote:
In comment 15574351 BlackLight said:


Quote:


flip a coin and have it come up heads ten times out of ten on purpose.


"this idiot" has a PhD in statistics from Harvard and is a professor at Stanford.


I already knew he was an idiot. No need to reconfirm it for me.

But seriously, tell Professor Pocket Protector to flip a coin ten times and have it come up heads.
RE: RE: RE: I want to see this idiot  
BH28 : 1/25/2022 3:52 pm : link
In comment 15574497 BlackLight said:
Quote:
In comment 15574395 Dr. D said:


Quote:


In comment 15574351 BlackLight said:


Quote:


flip a coin and have it come up heads ten times out of ten on purpose.


"this idiot" has a PhD in statistics from Harvard and is a professor at Stanford.



I already knew he was an idiot. No need to reconfirm it for me.

But seriously, tell Professor Pocket Protector to flip a coin ten times and have it come up heads.


Dr. Nerd says the earth is round? What is he Copernicus or something? What an idiot!
It really does depend upon who flips the coin...  
EricJ : 1/25/2022 3:55 pm : link
I have been able to replicate a scenario where the side that is facing down right before the flip will face up once it hits the ground.

What may be an interesting scenario then is to watch and track the referees to see when each guy flips the coin, does it end up heads or tails. They would likely flip it the same way each time.
......  
Route 9 : 1/25/2022 3:55 pm : link
People still give a shit about college degrees?
Why not have a coin with each teams logo on the sides  
DC Gmen Fan : 1/25/2022 4:00 pm : link
and whatever teams logo come up they win the toss
RE: I want to see this idiot  
Straw Hat : 1/25/2022 4:02 pm : link
In comment 15574351 BlackLight said:
Quote:
flip a coin and have it come up heads ten times out of ten on purpose.


+1.
RE: This guy...  
Jimmy Googs : 1/25/2022 4:05 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


haha, well done. At least posting with better humor these days...
RE: This guy...  
Osi Osi Osi OyOyOy : 1/25/2022 4:06 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


That’s all great, but what did he score on an internet IQ test?
Isn't that the same Mathematician  
Beer Man : 1/25/2022 4:10 pm : link
that set up the website for helping people pick winning lottery numbers (for a friendly fee of course)?
RE: Well, can someone use google  
ZogZerg : 1/25/2022 4:34 pm : link
In comment 15574491 ZogZerg said:
Quote:
to get the status for playoff coin flips?


55 Super Bowls

Tails = 29 times
Heads = 25 times

Pretty close.
Heads = 26 times  
ZogZerg : 1/25/2022 4:35 pm : link
Tails = 29 times
Flipping may not be flipping...  
TheEvilLurker : 1/25/2022 4:36 pm : link
It might be tossing, throwing the coin up in the air, without it going end over end.

I wonder if you can practice this enough to get the same outcome pretty regularly.
RE: Heads = 26 times  
The_Boss : 1/25/2022 5:05 pm : link
In comment 15574612 ZogZerg said:
Quote:
Tails = 29 times


Did the coin hit the turf though? Any breeze? Does it flip higher indoors vs outdoors? Was it a full moon?
RE: I you may be interested to hear that another theoretically 50/50  
section125 : 1/25/2022 5:14 pm : link
In comment 15574353 Festina Lente said:
Quote:
Occurrence that turns out to not be is the sex of a baby. Apparently, there is a slightly higher chance that the embryo will remain female than become male although im not sure of the actual statistic. I can guess the reason but i have never confirmed it.


Other way around. More males born at 105 to 100 rate.

By age 21, the numbers are the opposite, iirc.
It's very simple  
Mayo2JZ : 1/25/2022 5:16 pm : link
In OT each team gets the ball PERIOD. The coin toss just decides who receives the ball first. Eliminate the TD first wins the game. I never thought it was a good compromise when that was put it.
Sigh.  
81_Great_Dane : 1/25/2022 5:18 pm : link
The point is that the coin flip isn't governed strictly by probability. This is physics, not math. The coin flip is not strictly random because there are other factors involved that skew it from perfect randomness.

There's a physical object, the coin, that may or may not tend to land more often on one side. That coin then interacts with the environment: wind, the hand of the coin-flipper, etc. The flip isn't necessarily perfect, either; the side that is up when it's tossed tends to be the side that comes up when the coin lands. In basketball, they have cut back on the number of jump balls precisely because it's very hard to do a perfectly fair toss. Same is true for a coin.

If a solution is needed, it may just be not to let the person who calls the flip know whether the coin is starting with heads up or tails up. Or maybe no solution is needed at all. But it doesn't seem that hard to me to grasp that the theoretical coin flip isn't the same as a real coin flip, even if the difference is small.
RE: Sigh.  
Mayo2JZ : 1/25/2022 5:22 pm : link
In comment 15574700 81_Great_Dane said:
Quote:
The point is that the coin flip isn't governed strictly by probability. This is physics, not math. The coin flip is not strictly random because there are other factors involved that skew it from perfect randomness.

There's a physical object, the coin, that may or may not tend to land more often on one side. That coin then interacts with the environment: wind, the hand of the coin-flipper, etc. The flip isn't necessarily perfect, either; the side that is up when it's tossed tends to be the side that comes up when the coin lands. In basketball, they have cut back on the number of jump balls precisely because it's very hard to do a perfectly fair toss. Same is true for a coin.

If a solution is needed, it may just be not to let the person who calls the flip know whether the coin is starting with heads up or tails up. Or maybe no solution is needed at all. But it doesn't seem that hard to me to grasp that the theoretical coin flip isn't the same as a real coin flip, even if the difference is small.


No offense but "whatever"
If I'm  
liteamorn : 1/25/2022 5:41 pm : link
Involved in a coin toss with someone and they called Edges? I'd lose .
RE: This guy...  
Dennis : 1/25/2022 6:24 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


+1. LOL. Great post!
RE: This guy...  
GiantTuff1 : 1/25/2022 7:25 pm : link
In comment 15574365 Chris in Philly said:
Quote:
Ph.D. in Mathematical Statistics from Harvard
MacArthur Foundation "Genius" Fellowship
Elected member, American Philosophical Society
Fellow, American Mathematical Society
Elected member, National Academy of Sciences


BBI: Idiot!


Just LOL’ed so loud.
RE: Sigh.  
Festina Lente : 1/25/2022 9:14 pm : link
In comment 15574700 81_Great_Dane said:
Quote:
The point is that the coin flip isn't governed strictly by probability. This is physics, not math. The coin flip is not strictly random because there are other factors involved that skew it from perfect randomness.

There's a physical object, the coin, that may or may not tend to land more often on one side. That coin then interacts with the environment: wind, the hand of the coin-flipper, etc. The flip isn't necessarily perfect, either; the side that is up when it's tossed tends to be the side that comes up when the coin lands. In basketball, they have cut back on the number of jump balls precisely because it's very hard to do a perfectly fair toss. Same is true for a coin.

If a solution is needed, it may just be not to let the person who calls the flip know whether the coin is starting with heads up or tails up. Or maybe no solution is needed at all. But it doesn't seem that hard to me to grasp that the theoretical coin flip isn't the same as a real coin flip, even if the difference is small.


Shhhh... You're being too reasonable!
RE: RE: I you may be interested to hear that another theoretically 50/50  
Festina Lente : 1/25/2022 9:20 pm : link
In comment 15574689 section125 said:
Quote:
In comment 15574353 Festina Lente said:


Quote:


Occurrence that turns out to not be is the sex of a baby. Apparently, there is a slightly higher chance that the embryo will remain female than become male although im not sure of the actual statistic. I can guess the reason but i have never confirmed it.



Other way around. More males born at 105 to 100 rate.

By age 21, the numbers are the opposite, iirc.


Thanks, i had it backwards. That seems interesting to me. I looked it up and they believe that female babies have a slightly higher natural infant morality rate.
I'm waiting for our resident PhDs Debaser and Producer to weigh in...  
adamg : 1/25/2022 9:23 pm : link
.
RE: RE: Sigh.  
81_Great_Dane : 1/25/2022 9:57 pm : link
In comment 15574705 Mayo2JZ said:
Quote:
In comment 15574700 81_Great_Dane said:


Quote:


The point is that the coin flip isn't governed strictly by probability. This is physics, not math. The coin flip is not strictly random because there are other factors involved that skew it from perfect randomness.

There's a physical object, the coin, that may or may not tend to land more often on one side. That coin then interacts with the environment: wind, the hand of the coin-flipper, etc. The flip isn't necessarily perfect, either; the side that is up when it's tossed tends to be the side that comes up when the coin lands. In basketball, they have cut back on the number of jump balls precisely because it's very hard to do a perfectly fair toss. Same is true for a coin.

If a solution is needed, it may just be not to let the person who calls the flip know whether the coin is starting with heads up or tails up. Or maybe no solution is needed at all. But it doesn't seem that hard to me to grasp that the theoretical coin flip isn't the same as a real coin flip, even if the difference is small.



No offense but "whatever"
No offense taken.
I appreciated the post Dane  
adamg : 1/25/2022 10:30 pm : link
And CiP as well.

Education and comedy in two. Well done gents.
The coin flip to start a football game is random  
Producer : 1/26/2022 10:21 am : link
While under certain conditions and circumstances a coin flip *might* be random. Those conditions don't exist at the start of the football game.

The ref generally doesn't check what side he is flipping the coin from, he appears not to flip it in any particular manner, and he lets it drop to the ground.

RE: The coin flip to start a football game is random  
Producer : 1/26/2022 10:26 am : link
In comment 15575519 Producer said:
Quote:
While under certain conditions and circumstances a coin flip *might* be random. Those conditions don't exist at the start of the football game.

The ref generally doesn't check what side he is flipping the coin from, he appears not to flip it in any particular manner, and he lets it drop to the ground.


* might not
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