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    Probability question. Pi = ?? and also..




    Q: It is noted that 8% of abc students are left handed, if 20 students are randomly selected, calculate

    Probability that none of them are left handed.

    For this, my pi is 0.08 or 0.92?'

    and also

    Q: Do you agree that " if two events are mutually exclusive then these two events will be independent"? why?

    I know that mutually exclusive events means if event A happens, then Event B cannot happen, vice-versa.

    and independent events are events that do not affect the outcome of another.

    but how to put it in words as my English is not too good.
    Last edited by tiochaota; 05-17-2014 at 10:35 AM.

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    Re: Probability question. Pi = ??

    If 8% of the student population is left-handed, this means the probability of a randomly selected student not being left-handed is given by P = 10.08 = 0.92. Since all twenty randomly selected students should not be left-handed, the probability is then given by P = 0.920.920.92ׅ0.92 (to 20 terms) ≈ 0.1887.

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    Re: Probability question. Pi = ??

    Quote Originally Posted by Con-Tester View Post
    If 8% of the student population is left-handed, this means the probability of a randomly selected student not being left-handed is given by P = 1–0.08 = 0.92. Since all twenty randomly selected students should not be left-handed, the probability is then given by P = 0.920.920.92…0.92 (to 20 terms) ≈ 0.1887.
    but for my presentation of working, should it be 20C0 X 0.08^0 X (1-0.08)^20-0?
    Which also gets 0.1887.

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    Re: Probability question. Pi = ??

    There are many ways to get a probability, especially since you can always use compliments.
    Stop cowardice, ban guns!

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    Re: Probability question. Pi = ??


    Quote Originally Posted by tiochaota View Post
    but for my presentation of working, should it be 20C0 X 0.08^0 X (1-0.08)^20-0?
    Which also gets 0.1887.
    Sure, if you feel you have to use the full binomial formula. If you work it all out, 20C0 = 1, 0.08^0 = 1 and (1–0.08)^(20–0) = 0.92^20, giving P = 110.92^20 = 0.92^20 = 0.920.920.92…0.92 (to 20 terms) — i.e., the same answer I gave.

    My point here is that it’s fine if you want to learn the formula by rote, but my view is that a deeper understanding of probability is obtained when applying counting rules and/or pigeonhole principles whenever possible.

    This will answer the question you added later.
    Last edited by Con-Tester; 05-19-2014 at 02:36 AM.

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