Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
 You are Here: Home >< Maths

# Chances of landing 9 tails in a row? watch

1. (Original post by steve2005)
Why?
QI said so. I think somebody has done statistical analysis of people throwing coins and determined it. Probably someone from Cambridge as they seem to always do stupid stuff like that and report it to the media.
2. (Original post by Simplicity)
QI said so. I think somebody has done statistical analysis of people throwing coins and determined it. Probably someone from Cambridge as they seem to always do stupid stuff like that and report it to the media.
sounds like something you'd make a thread about tbh, it's THAT retarded.
3. (Original post by Totally Tom)
sounds like something you'd make a thread about tbh, it's THAT retarded.
With your intelligence I'm surprised your on this thread insulting me when you could be getting a field medal.
4. (Original post by Simplicity)
To be fair if a human flips a coin it will biased a bit towards heads. So the probability of flipping a coin and it landing on heads is not 50% more like 51%.
No, the probability of it landing on heads is extremely close to 50% (assuming you are more likely to land heads). Much closer to 50% than 51%.

I don't know the exact figure, but you're talking about loads of decimal places. e.g.

50.0000001%
5. (Original post by impervious)
I know how you feel. I havn't done stats in a month and for a second Poisson flashed through my mind...
Ha, I went binomial... XD
X~B(9,0.5)

I wish I could forget it! >.<
6. (Original post by Vivisteiner)
No, the probability of it landing on heads is extremely close to 50% (assuming you are more likely to land heads). Much closer to 50% than 51%.

I don't know the exact figure, but you're talking about loads of decimal places. e.g.

50.0000001%
Wikipedia disagrees: "coin tossing is fair to two decimals but not to three. That is, typical flips show biases such as .495 or .503".
7. You're seldom going to have a test in which the ratio between heads and tails is exactly equal though, are you?
8. it's more likely to land tails because the head is heavier than the tail, therefore it's not 50/50 chance.
9. (Original post by DFranklin)
Wikipedia disagrees: "coin tossing is fair to two decimals but not to three. That is, typical flips show biases such as .495 or .503".
Thats because of the bias of the person who flips the coin though, not a bias inherent in the coin.

(Original post by Wikipedia)
They have demonstrated that a mechanical coin flipper which imparts the same initial conditions for every toss has a highly predictable outcome

Your figures were only valid when a human tosses a coin. But we're trying to look at whether a coin is inherently biased to one particular side. Of course it is to some extent, but we're trying to work out how large that extent is.
10. (Original post by Vivisteiner)
Your figures were only valid when a human tosses a coin. But we're trying to look at whether a coin is inherently biased to one particular side. Of course it is to some extent, but we're trying to work out how large that extent is.
Then you're clearly changing the goalposts: Simplicity explicitly said he was talking about a human flipping a coin, you said he was wrong.
11. (Original post by DFranklin)
Then you're clearly changing the goalposts: Simplicity explicitly said he was talking about a human flipping a coin, you said he was wrong.
Ooops, my bad. Sorry about that.

I was more interested in the inherent nature of the coin, but I should've read his post more carefully.

Then again: I was right in saying it was nowhere near 51%, which was my main point.
12. (Original post by MazMaz)
it's more likely to land tails because the head is heavier than the tail, therefore it's not 50/50 chance.
surely that would depend entirely on the coin design and if true id imagine it wouldnt apply to all the coins in the world...
13. LLN, either way one side is going to land more than the other. We´re talking bout small numbers here anyway so lol.
14. (Original post by ashy)
I have a physics degree, and for a brief moment the binomial expansion drifted through my mind. Why? Stupid brain.

Well I suppose it is technically.
just it would be 9c0*0.5^0*0.5^9 which is 0.l5^9 yeah.

would like to know what OP's friend thinks it is though.
15. (Original post by Tallon)
would like to know what OP's friend thinks it is though.
Lol, he tried arguing that it was still 50/50... Saying that each coin toss is a separate chain of event(s), while I claimed it was 1/512
16. (Original post by Haz313)
Technically not.. If thrown an even number of times and it is perfectly 50/50.. in the Long run it should land an equal time on each side
Not if you toss it an odd number of times.
17. (Original post by Vivisteiner)
Not if you toss it an odd number of times.
Only just realised I had asked about 9 flips haha..
18. (Original post by Tallon)
Well I suppose it is technically.
just it would be 9c0*0.5^0*0.5^9 which is 0.l5^9 yeah.

would like to know what OP's friend thinks it is though.
Indeed it is, but there's no need for my brain to overcomplicate it
19. (Original post by Haz313)
Lol, he tried arguing that it was still 50/50... Saying that each coin toss is a separate chain of event(s), while I claimed it was 1/512
I think you might both be right sort of.

The actual 9th toss: the probability of it being tails is 0.5

However, the probability of getting 9 tails in a row is 1/512
20. (Original post by Haz313)
Lol, he tried arguing that it was still 50/50... Saying that each coin toss is a separate chain of event(s), while I claimed it was 1/512
My brother likes to argue when he's obviously wrong. When I ask him the odds of winning the lottery, he says "it's 50/50, you either win, or you don't" .

Reply
Submit reply
Turn on thread page Beta
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: July 31, 2009
Today on TSR

### Been caught plagiarising...

...for the 2nd time this year

### Mum says she'll curse me if I don't go to uni

Discussions on TSR

• Latest
Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.