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Math Help - Binomial probability.

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    Binomial probability.

    a survey is carried out on a computer network.the probability that a log on to the network is succesful is 0.97.find the probabilty that exactly six out of eight users that attempt to log on will do so successfully.
    x is bin(8, 0.97)
    P[6] = C(8,6) * 0.97^6 * 0.03^2 = 0.0209908945242108 is this correct or am i doing this completely wrong???
    Last edited by mr fantastic; July 17th 2011 at 01:21 AM. Reason: Re-titled.
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    Re: Probabilty help!!!!!!!!!!!!?

    Quote Originally Posted by university View Post
    P[6] = C(8,6) * 0.97^6 * 0.03^2
    Sounds good to me.
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    Re: Binomial probability.

    Quote Originally Posted by university View Post
    a survey is carried out on a computer network.the probability that a log on to the network is succesful is 0.97.find the probabilty that exactly six out of eight users that attempt to log on will do so successfully.
    x is bin(8, 0.97)
    P[6] = C(8,6) * 0.97^6 * 0.03^2 = 0.0209908945242108 is this correct or am i doing this completely wrong???
    The number of significant figures given is - sorry - absurd. Most questions state the accuracy required - check the question and round your answer accordingly.
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    Re: Binomial probability.

    Quote Originally Posted by mr fantastic View Post
    The number of significant figures given is - sorry - absurd. Most questions state the accuracy required - check the question and round your answer accordingly.
    No need to check the question the clue is in the precision of the log-on probability. This is given to two significant figures, no naively we might expect that we should give the answer two significant figures or 0.021.

    But wait I hear you cry, a probability of 0.97 indicates a range of possible values of 0.965 to 0.975 (give or take an end point). That gives a range for the answer of 0.0277 to 0.0150, so we have at best only one significant figure, so the answer should be truncated to 0.02.

    CB
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    Re: Binomial probability.

    Quote Originally Posted by CaptainBlack View Post
    No need to check the question the clue is in the precision of the log-on probability. This is given to two significant figures, no naively we might expect that we should give the answer two significant figures or 0.021.

    But wait I hear you cry, a probability of 0.97 indicates a range of possible values of 0.965 to 0.975 (give or take an end point). That gives a range for the answer of 0.0277 to 0.0150, so we have at best only one significant figure, so the answer should be truncated to 0.02.

    CB
    Aha .... but maybe the log-on probability is - unbelievably, perhaps - an exact probability ....
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    Re: Binomial probability.

    Quote Originally Posted by mr fantastic View Post
    Aha .... but maybe the log-on probability is - unbelievably, perhaps - an exact probability ....
    I'm sure that would violate some rule about how it should be written, but which I don't know!?

    CB
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