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Old Oct 31, 2009, 09:50 AM
drfarah
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Statistic (probability)

I want to know the answer of this question URGENTLY please:

Q:
State the number of possible outcomes if a fair dice is drown two times. Write down all the possible outcomes that give the following events and calculate then the probability such that:
a)The sum of the two tries is above 5

b) The draws have the same outcome.

Thanks a lot

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Old Oct 31, 2009, 11:30 AM   #2  
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There are 36 outcomes. List them out. 1,1; 1,2; 1,3; 1,4; 1,5; 1,6; .................... and so on.

If there were 3 dice, then there would be 6^3 outcomes. If there were 10 dice, there would be 6^10 outcomes. See the pattern?.

There is a quick way to find how many outcomes sum to more than 5.

That means they would have to sum to 6,7,8,9,10,11,12.

It is called a generating function.



If we expand this we get

Look at the exponents and their corresponding coefficients(numbers in front of the x's).

Look at the exponents larger than 5 and add up their coefficients. Each number it fron of the x is how many times that sum occurs. For instance, how many ways sum to 7?. The coefficient corresponding to x^7 is 6. There are 6 ways the two dice sum to 7. So, the probability we get a sum of 7 is 6/36=1/6.
See?. Do this with your case and divide by 36 to fnd the probability. Or, you can list them out and count them up. But I do not like brute force. Especially with counting problems. It defeats the purpose.
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Old Nov 1, 2009, 03:01 AM   #3  
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So the pr(A), where A is the sm of the two tries above 5 = 27/36

and the probability of the second Q is 6/36 (the probabilti of the two of tries are equal)

Thank you very much for your patient and your helpful answers.
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Old Nov 1, 2009, 04:02 AM   #4  
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I got 26/36!?

I used a probability table.
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Old Nov 1, 2009, 04:20 AM   #5  
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Yes, Unknown has it. Just add up the coefficients.

They sum to 26

So, we ave 26/36=13/18
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Old Nov 1, 2009, 10:40 AM   #6  
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what is the probability of getting one six if a die is thrown four times?
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Old Nov 1, 2009, 10:44 AM   #7  
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if a die is thrown four times what is the probability that the nunber is six?
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Old Nov 1, 2009, 09:17 PM   #8  
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Start your own thread sakidbzu. And post the answer you think is good.
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Old Nov 2, 2009, 12:22 AM   #9  
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oh ok thanks,,
and the The draws have the same outcome will it be 6/36?
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Old Nov 2, 2009, 12:31 AM   #10  
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Yes, exactly! Well done!
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