# Dice and probability

1. Apr 21, 2013

### ParisSpart

Pour an ordinary dice 129 times and let X the sum of all indications that it brings.

Let p=P(X<=12)

What is the minimum upper bound for the probability p resulting from inequality of Chebyshev;

Note: The probability density of X is symmetric about the mean value of X

how i can find the fX(x) of the sum of all indications that brings the dice if we roll it 129?

2. Apr 21, 2013

### Ray Vickson

The question is unclear. Do you toss a single die 129 times (each time getting a number from 1 to 6), or do you toss a pair of dice 129 times (each time getting a number from 2 to 12)?

Anyway, you need to show your work first before we can help.

3. Apr 21, 2013

### ParisSpart

we toss a dice 129 times, but i cant think how to find the E(X) and Var(X) of this thats why i aksed for help...
i will estimate any sum? from 1 to 129?

4. Apr 21, 2013

### Ray Vickson

You still have not described your problem in meaningful terms: the words "a dice" are contradictory. The "a" means one but the word "dice" means 2 or more. If you toss just one cube with faces numbered 1--6 you are tossing one die (NOT dice); if you toss two such cubes (giving a total from 2--12 in each toss) you are throwing dice = more than one die. So, which do you mean?

5. Apr 22, 2013

### ParisSpart

we toss one dice 129 times not two...

6. Apr 22, 2013

### Ray Vickson

No, you don't. You toss one die 129 times. You are tossing a DIE, not DICE.

7. Apr 22, 2013

### ParisSpart

yea anyway , how i am gonna estimate the expected value of the random variable X which is the sum of all outcomes i am confused