Find the probability distribution of Y in two throws of two dice, where Y represents the number of times a total of 9 appears.
When two fair dice are thrown there are total 36 possible outcomes.
In our question, we are throwing two dice 2 times
∵ Y denotes the number of times, a sum of two numbers appearing on dice is equal to 9.
∴ Y can take values 0,1 or 2
Means In both the throw sum of 9 is not obtained, in one of throw of two dice 9 is obtained and in both the throws of two dice a sum of 9 is obtained.
∵ (3,6) (6,3) (5,4) and (4,5) are the combinations resulting in sum = 9
Let A denotes the event of getting a sum of 9 in a throw of 2 dice
∴ P(A) = probability of getting the sum of 9 in a throw of 2 dice is
And P(A’) = probability of not getting the sum of 9 in the throw of 2 dice =
Note: P(AՈB) = P(A)P(B) where A and B are independent events.
P(Y = 0) = P(A’)×P(A’) =
P(Y = 1) = P(A)×P(A’)+ P(A’)×P(A)+ =
P(Y = 2) = P(A)×P(A) =
Now we have pi and xi.
∴ The required probability distribution is:-