# Thread: Suppose a non bias coin was tossed two times?

1. ## Suppose a non bias coin was tossed two times?

how would you do a random variable problem like this

suppose a non bias coin was tossed two times

2. Originally Posted by jim1174
how would you do a random variable problem like this

suppose a non bias coin was tossed two times
Well... let $\displaystyle x$ be the random variable. You could make it stand for the number of times heads appeared.

$\displaystyle Pr(X=x)$ would then be the probability that x heads appeared.

$\displaystyle Pr(X=0) = 1-\left(\frac{1}{2}\right)^2 = \frac{3}{4}$xxx
$\displaystyle Pr(X=1)=\frac{1}{2}$
$\displaystyle Pr(X=2) = \left(\frac{1}{2}\right)^2 = \frac{1}{4}$

Since the coin is non-biased these same probabilities would appear if you set $\displaystyle x$ as the number of tails that appeared.

Is this what you wanted?

3. ## Error

DividyBy0,

Shouldn't it be $\displaystyle Pr(X=0) = \left(1-\frac{1}{2}\right)^2 = \frac{1}{4}$, not $\displaystyle Pr(X=0) = 1-\left(\frac{1}{2}\right)^2 = \frac{3}{4}$ ?

--Kevin C.

4. yeah, you're right