Thread: Probability Mass Function?

1. Probability Mass Function?

I need help with this probability question please...i have no idea what I am doing here....thanks in advance...

A die is rolled 4 times. Let X and Y be the number of appearances of 1 and 6 respectively. Find the joint PMF of (X, Y).

2. Originally Posted by rangergiya
I need help with this probability question please...i have no idea what I am doing here....thanks in advance...

A die is rolled 4 times. Let X and Y be the number of appearances of 1 and 6 respectively. Find the joint PMF of (X, Y).
If you know the multinomial distribution use that with possible outcomes 1, 6, other; with probabilitirs 1/6, 1/6, 2/3 respectivly.

Otherwise list all the possible outcomes (1, 6, other) compute their probabilities and sum those with the same number 1's and 6's.

CB