odds of flipping a coin.

touch · 9 Mar 2009 at 19:10

My brother just asked me this question:

If you flip a coin the first time and get heads, what are the chances of it happening again

Obviously, i answered 50:50.
He says that there is a slight statistical advantage to it being heads again next time because one side of the coin could be heavier and you cant tell from the first flip. So i thought about what he said and decided that he's wrong. Even if the coin was slightly weighted to one side, the flip is still truely random unless you can find a way to flip the coin with the same power and catch it at the same height/time ever go (need to use some sort of flipping machine).

So we are now in the middle of an argument. Does a slightly off balance coin produce random outcomes if it is flipped by hand?

Bes · 9 Mar 2009 at 19:12

Yes it would. The heavier side is more likely to be facing downwards.

Millwall.FC · 9 Mar 2009 at 19:12

Your right, he's wrong.

iamdjdz · 9 Mar 2009 at 19:12

You also have to take into account that it can land on it's side so the odds, of a fair coin are more like:

heads 49.95%
tails 49.95%
side 0.1%

fiveub · 9 Mar 2009 at 19:13

Well if it is true that it is off balance... Then there will be more of a percent than 50 out of 50.

Thinking about it, when flipping, surely the speed of the rotation would not matter what side is heavier? I am not very good at science so I could be totally wrong!

Sinque · 9 Mar 2009 at 19:13

Totally random if the force etc are not exactly the same.

If in measured conditions such as air resistance, weight of coin, force of flip, height blah blah blah you could ensure it landed on the same side 100% of the time.

strudey · 9 Mar 2009 at 19:13

Millwall.FC said:
Your right, he's wrong.

Nah, in the real world, he's right.

yhack · 9 Mar 2009 at 19:13

Have you taken into account the wind speed and direction?

Aloreth · 9 Mar 2009 at 19:14

iamdjdz said:
You also have to take into account that it can land on it's side so the odds, of a fair coin are more like:

heads 49.95%
tails 49.95%
side 0.1%

thats got to be the dumbest thing i have ever heard!

Bes · 9 Mar 2009 at 19:14

iamdjdz said:
You also have to take into account that it can land on it's side so the odds, of a fair coin are more like:

heads 49.999995%
tails 49.99999995%
side 0.0000001%

Fixed assuming both sides are the same weight

aayzof · 9 Mar 2009 at 19:14

No idea, I know nothing about physics and nothing about maths.

iamdjdz · 9 Mar 2009 at 19:15

Aloreth said:
thats got to be the dumbest thing i have ever heard!

It was a joke

But this one time a coin i flipped landed on its side.

RandomTom · 9 Mar 2009 at 19:15

0.9r = 1

fiveub · 9 Mar 2009 at 19:16

What if you flipped a coin, kept it covered in your hand. What would it be then, heads or tails?

qwerty · 9 Mar 2009 at 19:16

Coins are not perfectly weighted. They will always be slightly biased to one side. However, the information on the weighting of the coin you can gain from one toss is tiny. If you flipped it a billion times and it came out 51% heads, you could start considering the idea that the coin is biased to land on heads.

Jokester · 9 Mar 2009 at 19:19

Magical Trevor said:
What if you flipped a coin, kept it covered in your hand. What would it be then, heads or tails?

Schrödinger's cat says meow, I mean both.

fiveub · 9 Mar 2009 at 19:20

Jokester said:
Schrödinger's cat says meow, I mean both.

I would say it would be heads, if you had a double headed coin that is!

Spuff Monkey · 9 Mar 2009 at 19:21

Ask your brother if he's been watching QI

Sweetloaf · 9 Mar 2009 at 19:28

Magical Trevor said:
What if you flipped a coin, kept it covered in your hand. What would it be then, heads or tails?

Yes.

GeForce · 9 Mar 2009 at 19:43

Spuff Monkey said:
Ask your brother if he's been watching QI

Exactly

On which side it lands depends a lot upon which side it starts.