1. ## Binomial conditional probability.

A fair coin is tossed 5 times. What is the probability of obtaining exactly 2 heads if it is known that at least 1 head appeared?

2. ## Re: binomial probability help please

What is the probability of exactly one (1) "heads" in four tosses? Are you sure it's trickier than that? If so, why?

3. ## Re: binomial probability help please

what do you mean?

4. ## Re: Binomial conditional probability.

Originally Posted by mtingt
A fair coin is tossed 5 times. What is the probability of obtaining exactly 2 heads if it is known that at least 1 head appeared?
Let X be the random variable 'Number of heads'.

Calculate $Pr(X = 2 | X \geq 1)$ using the usual formula for conditional probability.