Probability question, who can help?

2011-09-10 2:41 pm
A pair of dice are rolled. Let Y denote the sum showing uppermost.

Display the probability distribution of Y in tabular form.

回答 (2)

2011-09-10 5:43 pm
✔ 最佳答案
Total number of possible outcomes = 6^2 = 36
The outcomes are listed out here below
(1,1)(1,2)(1,3)(1,4)(1,5)(1,6)
(2,1)(2,2)(2,3)(2,4)(2,5)(2,6)
(3,1)(3,2)(3,3)(3,4)(3,5)(3,6)
(4,1)(4,2)(4,3)(4,4)(4,5)(4,6)
(5,1)(5,2)(5,3)(5,4)(5,5)(5,6)
(6,1)(6,2)(6,3)(6,4)(6,5)(6,6)
Probability distribution of Y
... Y ... Probability
... 2 ... 1/36
... 3 ... 2/36
... 4 ... 3/36
... 5 ... 4/36
... 6 ... 5/36
... 7 ... 6/36
... 8 ... 5/36
... 9 ... 4/36
...10 ... 3/36
...11 ... 2/36
...12 ... 1/36
TOTAL: 36/36 = 1.0
2011-09-10 10:31 pm
I do not think your teacher wants you to show a multiplication table, but you can draw that out so you can get an idea of what you are dealing with.

Essentially you need to figure out how many combinations can be used to come up with each number... So for 2, there is only one combination - which is 1 and 1 on the dice.
Meanwhile a number like 7 has the highest probability because it has multiple combinations - 3 and 4, 5 and 2, 6 and 1.

I am not sure of the formula for this. I believe you are supposed to use a combination formula that is something like
n-1 (n!) something like that - its been like 4 years since i took a statistics class. If you are having a hard time, be sure to talk to your teacher because thats one of the classes you either understand or you dont


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