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Math Help - Binomial probability question

  1. #1
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    here is another one...will appreciate any help ...

    A recent article in the paper claims that business ethics are at an all-time low. reporting on a recent sample, the paper claims that 30% of all employees believe their company CEO has low ethical standards. Suppose 20 of a company's employees are randomly sampled. Assuming the paper's claim is correct, find the probability that more than 8 but fewer than 12 of the 20 sampled believe the company's CEO has low standards.
    Last edited by mr fantastic; April 14th 2009 at 10:16 PM. Reason: Moved from another thread and edited.
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  2. #2
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    Well you know the probability and number or trials (n), so it's just a case of using the binomial distribution formula to calculate P(X=9) + P(X=10) + P(X=11). Are you able to find the answer now?
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  3. #3
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    The binomial distribution formular i know is the one you helped on the other problem...I tried to use that but I dont get the solution. if you can help me more i will really appreciate....
    Thanks
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  4. #4
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    Hello Allenge
    Quote Originally Posted by Allenge View Post
    here is another one...will appreciate any help ...

    A recent article in the paper claims that business ethics are at an all-time low. reporting on a recent sample, the paper claims that 30% of all employees believe their company CEO has low ethical standards. Suppose 20 of a company's employees are randomly sampled. Assuming the paper's claim is correct, find the probability that more than 8 but fewer than 12 of the 20 sampled believe the company's CEO has low standards.
    The probability of 'success', p = 0.3, where a 'success' is that an individual employee chosen at random believes that the CEO has low standards. The probability of 'failure', q = 0.7. The experiment (choosing an employee and determining their views about the CEO) is repeated n times, where n = 20.

    The probability of r successes out of n is \binom{n}{r}p^rq^{n-r}

    You need to calculate this probability when n = 20 and r = 9, 10 and 11 in turn, and add these three results together.

    If my working is correct, the answer is 0.1082 (4 d.p.)

    Grandad
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