Is it true that coin flips are always 50-50?

[matt grime]

A stastician would call them, probably, independent. The mutaully exclusivity is neither here nor there.

 

[Erazman]

haha this is the funniest thread I've ever read in my LIFE.
This is logic the average 8 year old would figure out.
I'm going to jump off a bridge. If my chance of living is 50/50, and i survive
then for sure next time will be death!

LOL

 

[phyti]

lets lay it to rest

Alright, I've been trying to convince my friend that the outcomes of a coin flip x times in a row affects the x+1'th time. If you flip a coin 4 times and they are all heads, the 5th time is more likely to be a tail because if the coin is even, over time there should be as many tails as there are heads. I even tried to prove it to him using math:
P(5 heads in a row) = .5^5 = 0.03125
P(4 heads in a row) = .5^4 = 0.0625

The system of coin tossing has no memory and therefore is time independent.
Any sequence of of n coins can occur but you cannot predict WHEN!

 

[sjoly]

Peng is right. I'm having to approach this is simple terms..I'm by no means an engineer. But anyway, the odds of 2 heads in a row are .5x.5. 3 heads=.5x.5x.5..et cetera. OTHERWISE, the odds of having a roulette ball hit black 10 times in a row would be the same as it hitting just one red (out of ten). Been to Vegas? Stand there and bet black all night and you'll walk away with approx. 50% of your bets. When I go to Vegas, I wait for 7 black hits in a row (or red)..and then I start betting on the other color.
Now I could go on forever..but why doesn't everyone simply bet 1,2,3,4,5,6 on the lottery. Technically, those numbers coming up have the same chance as any other combination...but there is more to it than that. I don't know what..but if I did, it would probably be easy to hit the lottery. I'm rambling. So I'll stop. But Peng is most definitely correct. Now it is true that there is a 50/50 probability each time..but only a 25% prob. on round number 2 for the same result. And so on.

 

[LukeD]

Wow, crazy zombie thread and horrible misunderstanding of probability. It took me a while before I figured out what sjoly was even trying to say because his post contains several contradictions in its own explanation.

 

[DaveC426913]

This is logic the average 8 year old would figure out.
I'm going to jump off a bridge. If my chance of living is 50/50, and i survive
then for sure next time will be death!

Alas, my 22-year-old actually thinks this way.

"I might die from smoking and I might not, just like I might step outside and get hit by a car or I might not. The chances are 50-50, so why worry?"

Couple that with a three-second attention span for critical analysis of any sort, and I mourn for our country's future.

 

[Dragonfall]

Actually flipping a coin twice, if actually done, do not produce independent events, because the movement of the first flip disturbs the air (or other factors) in such a way that it might influence the outcome of the second flip. To ensure that they are independent, assuming it takes 1 second to perform the experiment, you must place the coins 2 light-seconds apart, then from the middle send a signal to both coins to be flipped simultaneously.

Of course for all PRACTICAL purposes they are independent.

 

[Hurkyl]

This thread is old and the necromancer is spreading misinformation; I think it's time to close it.