Please, Please help!!! Desperate to get this project done...

Arwyn

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Apr 28, 2010
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I need help to find the Mean for the theoretical probability of rolling two twelve-sided dice. I already have the experimental data set to do that... I just need the formula, or some way of knowing how to calculate this. I only have the formula for calculating the probability for tossing two coins.... I don't see how I would do this for rolling two twelve sided dice, please help! Again, I need to know how to get the mean for the theoretical probability of rolling two twelve-sided dice.

Thanks,
Sarah
 
Arwyn said:
I need help to find the Mean for the theoretical probability of rolling two twelve-sided dice. I already have the experimental data set to do that... I just need the formula, or some way of knowing how to calculate this. I only have the formula for calculating the probability for tossing two coins.... I don't see how I would do this for rolling two twelve sided dice, please help! Again, I need to know how to get the mean for the theoretical probability of rolling two twelve-sided dice.

Thanks,
Sarah

If rolled two 6 sided dice - how many ways you can do that?
 
I guess 4... but I still don't know how to get the mean. I need to do a probability distribution graph for rolling two twelve sided dice (both for theoretical and experimental), but to do that I need the mew... I only know how to get the mew, or mean, from tossing two coins, what is the formula for doing so with rolling 2 twelve sided dice? If I'm looking for Heads (coin) it is: the sum of H(P(h)) and from there I can get my standard deviation.... I'm completely lost with how to do this for the dice...
 
Sorry to say, but really there is no neat formula.
With twelve sided dice, there are 144 possible outcomes (ordered pairs).
There is one way to get a sum of two. There are two ways to get a sum of three.
There are eleven ways to get a sum of twelve. etc
You must find the number of ways to get each sum from two to twenty-four.
The nice thing is that it is symmetrical about sum 13.
 
Alright, so, if I know that the probability of getting a sum of 13 is 12/144, how do I get the mean for the theoretical probability?... for coins it is 0(1/4)+1(2/4)+2(1/4)=0+2/4+2/4=4/4=1 but for rolling 2 twelve sided dice? Would it be easier to try and find the probability of rolling a set of numbers than the sum? How do I calculate the mean in either case?
 
Arwyn said:
Alright, so, if I know that the probability of getting a sum of 13 is 12/144, how do I get the mean for the theoretical probability?... for coins it is 0(1/4)+1(2/4)+2(1/4)=0+2/4+2/4=4/4=1 but for rolling 2 twelve sided dice? Would it be easier to try and find the probability of rolling a set of numbers than the sum? How do I calculate the mean in either case?
As with any mean: \(\displaystyle \sum\limits_{x = 2}^{24} {x \cdot P(x)} = 2 \cdot \frac{1}{{144}} + 3 \cdot \frac{2}{{144}} + \cdots + 13 \cdot \frac{{12}}{{144}} + \cdots + 24 \cdot \frac{1}{{144}}\)
 
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