(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Suppose that a fair coin is tossed repeatedly until a head is obtained for the first time.

(a) What is the expected number of tosses that will be required?

(b) What is the expected number of tails that will be obtained before the first head is

obtained?

2. Relevant equations

E(x)= from -infinity to +infinity (continuous case)

E(x)= for all x (discrete case)

3. The attempt at a solution

p=head=1/2

q=tail=1-p=1/2

Pr(X>1)=1 for n=2,3,.....

Pr(X>n)=q^{n-1}

E(x)=1/(1-q)=1/p=2

-if only 2 tosses are expected to obtain a head then only one tail would be obtained before a head

-does this make sense???

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# Homework Help: Tossing a fair coin

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