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Math Help - Binomial probability

  1. #1
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    Binomial probability

    A poll shows that 70% of all voters approve of the mayor's work. On three separate occasions a pollster selects a voter at random. What is the probabilty that on exactly one of these three occasions the voter approves of the mayor's work?

    Could someone please explain this as easy as possible?

    Vicky.

    Thanks.
    Last edited by mr fantastic; November 12th 2009 at 02:04 AM.
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  2. #2
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    Quote Originally Posted by Vicky1997 View Post
    A poll shows that 70% of all voters approve of the mayor's work. On three separate occasions a pollster selects a voter at random. What is the probabilty that on exactly one of these three occasions the voter approves of the mayor's work?

    Could someone please explain this as easy as possible?

    Vicky.

    Thanks.
    If X is the random variable 'number of voters who approve of the mayor' then X ~ Binomial(n = 3, p = 0.7). Calculate Pr(X = 1).
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    Quote Originally Posted by mr fantastic View Post
    If X is the random variable 'number of voters who approve of the mayor' then X ~ Binomial(n = 3, p = 0.7). Calculate Pr(X = 1).

    Thanks for your help. But I don't know what Binomial probability means.
    But I could think of three cases

    1st person 2nd person 3rd person

    1 approve disapprove disapprove

    2 disapprove approve disapprove

    3 diapprove disapprove approve


    Could you please help me a little more?

    Vicky.



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    Quote Originally Posted by Vicky1997 View Post
    Thanks for your help. But I don't know what Binomial probability means.
    But I could think of three cases

    1st person 2nd person 3rd person

    1 approve disapprove disapprove

    2 disapprove approve disapprove

    3 diapprove disapprove approve


    Could you please help me a little more?

    Vicky.


    Calculate the probability of each outcome. Add the results. That's the answer.
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    Quote Originally Posted by mr fantastic View Post
    Calculate the probability of each outcome. Add the results. That's the answer.
    I think I got the answer.

    7/10 X 3/10 X 3/10 = 63/1000

    3/10 X 7/10 X 3/10 = 63/1000

    3/10 X 3/10 X 7/10 = 63/1000

    189/1000

    Thanks!!!
    Last edited by Vicky1997; November 14th 2009 at 09:46 PM.
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    Quote Originally Posted by Vicky1997 View Post
    I think I got the answer.

    7/10 X 3/10 X 3/10 = 63/1000

    3/10 X 7/10 X 3/10 = 63/1000

    3/10 X 3/10 X 7/10 = 63/1000

    189/1000

    Thanks!!!
    Correct. (And you're welcome).
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