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Homework Help: Binomial distribution formulae?

  1. Aug 27, 2009 #1
    1. Let the p.m.f. pf M be defined by f(m)=x/8, x=1,3,4. What is the mean of M?



    2. n!/n-r*p^n*(1-p)^n-r



    3. 3!*1/3^3*2/3^2=.59 This is not the correct answer!
     
    Last edited: Aug 28, 2009
  2. jcsd
  3. Aug 28, 2009 #2

    D H

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    Staff Emeritus
    Science Advisor

    Re: p.m.f.

    That isn't the correct answer because you aren't using the correct expression for calculating the mean. Why are you using the binomial distribution formulae?
     
  4. Aug 28, 2009 #3
    Re: p.m.f.

    D.H.

    What distribution of equation should I use? I'm from the behavioral sciences and I
    am not familiar with this problem.
     
  5. Aug 28, 2009 #4

    HallsofIvy

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    Science Advisor

    Re: p.m.f.

    The problem tells you what to use! The probability is given by f(m)=x/8, x=1,3,4. That is, f(1)= 1/8, f(3)= 3/8 and f(4)= 4/8= 1/2. And the mean is given by [itex]\sum x f(8)[itex].
     
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