Question
Find the probability distribution of number of doublets in three throws of a pair of dice.
Solution
Let X denote the number of doublets. X can take the value 0, 1, 2, or 3.
Possible doublets are (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)
Probability of getting a doublet = 
Probability of not getting a doublet = 
Now, P(X = 0) = P(no doublet) = 
and 
∴ the required probability distribution is
