Probability / Statistics question

[Z-Juice]

Hopefully you guys can help me out with a fairly simple statistics problem:

Three fair dice are rolled together. Let X be the random variable denoting the sum of all three top faces. Write out the pmf and cdf.

I know what a pmf and cdf are, but all of the examples in class and other problems we've done have been done knowing what the pmf and cdf are and then computing the probabilities of X. I'm having trouble approaching this problem because it's the other way around.

 

[Yaraelpoof.png]

Find q? And do it that way?

 

[TurquoiseGrizzly]

Skiing is always the answer

 

[Lus146]

Speak english please.

 

[Blurst]

Skiing is always the answer

I completely and whole heartedly agree, OP should certainly go skiing to alleviate the problem.

 

[Z-Juice]

I completely and whole heartedly agree, OP should certainly go skiing to alleviate the problem.

That's the plan if I can get this assignment done.

 

[Z-Juice]

Find q? And do it that way?

I don't know what q is, and this question is not supposed to be very complicated. Out of the few distributions we've learned (Geometric, Bernoulli, Binomial, Poisson), I think you just need to pick one to find which models the individual results of each die, which is your pmf, and then integrate the pmf to get the cdf. I'm confused because the Geometric, Bernoulli, and Binomial distributions only model "successes or failures", no more than two options while you can roll a 1,2,3,4,5 or 6 with a die.

 

[DrZoidberg]

I haven't done this in a while, especially not in this context. But it's a bernoulli thing right?

http://en.wikipedia.org/wiki/Multinomial_distribution

Could be totally wrong. I never really did this much in this sort of problem.