1. ## Statistics

I had a test today. Heres one of my questions. Can someone do it, because im not sure if I got it right, and I'd like to know now.

You have two different dice. One die has a 1 and five 3's.
The next die has four 2's and two 6's.

Like this:

Die 1- 133333
Die 2- 222266

Set up this table:
X __ __ __ __
p(X) __ __ __ __

What is the mean?
What is the standard deviation?

For the X's, I put 3, 5, 7, 9
Can someone do this so I can see if im right with everything? I'd really appreciate it! thanks

2. Originally Posted by Morgan82
I had a test today. Heres one of my questions. Can someone do it, because im not sure if I got it right, and I'd like to know now.

You have two different dice. One die has a 1 and five 3's.
The next die has four 2's and two 6's.

Like this:

Die 1- 133333
Die 2- 222266

Set up this table:
X __ __ __ __
p(X) __ __ __ __

What is the mean?
What is the standard deviation?

For the X's, I put 3, 5, 7, 9
Can someone do this so I can see if im right with everything? I'd really appreciate it! thanks
So X is the random variable the sum of the total of the two dice?

Looking at the sample space and using (number of favourable outcomes)/(total number of outcomes), it's not hard to see that

Pr(X = 3) = 4/36 = 1/9.
Pr(X = 5) = 20/36 = 5/9.
Pr(X = 7) = 2/36 = 1/18.
Pr(X = 9) = 10/36 = 5/18.

Get mean and sd in the usual way.

3. Originally Posted by mr fantastic
So X is the random variable the sum of the total of the two dice?

Looking at the sample space and using (number of favourable outcomes)/(total number of outcomes), it's not hard to see that

Pr(X = 3) = 4/36 = 1/9.
Pr(X = 5) = 20/36 = 5/9.
Pr(X = 7) = 2/36 = 1/18.
Pr(X = 9) = 10/36 = 5/18.

Get mean and sd in the usual way.

Thanks alot! Thats how I did it, now I feel alot better. Thanks again!