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Homework Statement
You flip a fair coin until you get the same face twice in a row.
What is the probability that you stop on an even number of tosses?
Example: Probability of taking less than 6 tosses to stop is 15/16
In general, the probability of stopping on the nth toss is 1/2^(n-1)
Homework Equations
Example: Probability of taking less than 6 tosses to stop is 15/16
In general, the probability of stopping on the nth toss is 1/2^(n-1)
The sum of probabilities as n (the number of tosses) grows is 1.
The Attempt at a Solution
Pr(2 tosses) = 1/2
Pr(3 tosses) = 1/4
Pr(4 tosses) = 1/8
In general there are only two sequences for n tosses that end on the nth toss.
Either it starts with tails and alternates until the last 2 tosses or it starts with
heads and alternates until the last 2 tosses.
Example
HTHH
THTT
Only 2 sequences that end on the 4th toss.