Let p and q denote the events of failure and success, respectively.

We know that, a random variable X (=0,1, 2,…., n) is said to have Binomial parameters n and p, if its probability distribution is given by

Where, q = 1-p

And r =0,1,2,…..n

In an experiment of tossing a coin three times, we have n=3 and random variable X can take values r =0,1,2 and 3 with and

So, we see that in the experiment of tossing a coin three times, we have random variable X which can take values 0,1,2 and 3 with parameters n=3 ad

Hence tossing of a coin 3 times is a Binomial distribution.