Originally Posted by

**usagi_killer** Hi, I am currently stuck on this extended response question from my book, I really don't know how to do the parts of the questions, could anyone help me? Thanks

You are given two un-biased dice, one painted red and one painted blue. You roll the dice and you record the numbers showing on each die. Let R by the random variable for the red die and B the corresponding random variable for the blue die.

(a) Write down the probability distribution for each of the random variables R and B.

(b) Write down the joint probability distribution, Pr(R,B). That is, the probability of obtaining, in the one roll, a specic value for R and a specic value for B.

(c) Use the joint distribution to deduce the probability distribution for R - B.

(d) Hence calculate the mean and standard deviation for R - B.