Problem 6E

Two dice are rolled. Let X = 1 if the dice come up doubles and let X = 0 otherwise. Let Y = 1 if the sum is 6. and let Y=0 otherwise. Let Z = 1 if the dice come up both doubles and with a sum of 6 (that is, double 3), and let Z = 0 otherwise.

a. Let px denote the success probability for X. Find pX

b. Let pY denote the success probability for Y. Find py.

c. Let pz denote the success probability for Z. Find pz.

d. Are X and Y independent?

e. Does pz = PXPY

f. Does Z = XY? Explain.

Answer:

Step 1 of 6:

(a)

In this question, we are asked to find the success probability for and hence .

Two dice are rolled.

Let if the dice come up doubles and let otherwise.

Let if the sum is 6. and let otherwise.

Let if the dice come up both doubles and with a sum of 6, and let otherwise.

Let is the outcome of rolling the first dice where is the number from to that die will show.

Let is the outcome of rolling the second dice where is the number from to that die will show.

Dice are rolled in the pairs , we have of such pairs.

Since when the dice come up doubles, then the outcomes which contribute success are .

Hence number of outcomes where dice come up doubles =

Therefore the success probability is

=

Hence the success probability for () is .