# You roll three dice, and you define the random variable #X# as the number of heads obtained. What are all possible values of the random variable #X#?

##### 1 Answer

Dec 17, 2014

I believe you mean either 'you flip a coin three times' or 'you flip three coins'.

X is called a 'random variable' because before we flip the coins we don't know how many heads we are going to get. But we can say something about all the *possible* values for X.

Since each flip of a coin is independent from other flips, the possible value of the random variable X are {0, 1, 2, 3}, i.e. you could get 0 heads or 1 head or 2 heads or 3 heads.

Try another one where you think about four tosses of a die. Let random variable Y denote the number of 6s in four tosses of a die. What are all the possible values of random variable Y?