Flipping coins

Mark R

Diamond Member
Oct 9, 1999
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Let's say you flip a coin repeatedly - it's a fair coin, and let's assume it never lands on its edge. So, 50% of tosses are heads, and 50% tails.

(1) How many tosses, on average, would you need to make before you get a sequence of Heads, Tails, Tails?

In other words, if you tossed: Heads, Tails, Heads, Tails, Heads, Tails, Tails - you would score this as 7; and Heads, Tails, Tails as 3

(2) How many tosses, on average, would you need to make before you get a sequence of Tails, Heads, Heads?

(3) How many tosses, on average, would you need to make before you get a sequence of Tails, Tails, Tails?

(4) How many tosses, on average, would you need to make before you get a sequence of Heads, Tails, Heads?

(5) A friend challenges you to a 'race'. You each choose a sequence. An independent third party tosses the coin. The winner is the the person whose sequence comes up first. Is there a sequence or sequences that you can choose that would maximize your chances of winning?

 

Leros

Lifer
Jul 11, 2004
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A coin flip is not 50/50, its 49/51. I forget which side has favor though.
 

jakedeez

Golden Member
Jun 21, 2005
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Originally posted by: Leros
A coin flip is not 50/50, its 49/51. I forget which side has favor though.

Well that maybe, but for purposes of his homework, lets assume its 50/50....
 

naldo

Golden Member
Aug 5, 2001
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If its 50/50 I dont think theres actually a way to determine any of the thing you mentioned.
 
Dec 10, 2005
27,960
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Originally posted by: naldo
If its 50/50 I dont think theres actually a way to determine any of the thing you mentioned.

You could make a tree diagram and multiply probabilities.
 

jakedeez

Golden Member
Jun 21, 2005
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Originally posted by: naldo
If its 50/50 I dont think theres actually a way to determine any of the thing you mentioned.

Sure there is, he isn't asking a fixed number, he is asking averages and P(x) of events, it is his prob. homework.