Binomial distribution formulae?

[morr485]

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!

 

[D H]

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?

 

[morr485]

D.H.

What distribution of equation should I use? I'm from the behavioral sciences and I
am not familiar with this problem.

 

[HallsofIvy]

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]