Binomial conditional probability.

**mtingt** · November 12th 2011, 08:31 PM

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?

**TKHunny** · November 12th 2011, 08:41 PM

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

**mtingt** · November 12th 2011, 08:44 PM

what do you mean?

**mr fantastic** · November 13th 2011, 10:49 AM

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.

Thread: Binomial conditional probability.