Q on pgf- Variance of a function

[Sonal7]

I am trying to find Var (X) for 1/ln2 {ln(2/(2-t)}
I have dont some working but its turning to a real mess.

I would appreciate some help.

 

[nasi112]

So you mean, the probability density function of [MATH]X[/MATH] is

[MATH]f(t) = \frac{1}{\ln 2} \cdot \ln \frac{2}{2 - t}[/MATH]
If this is correct, what is the interval of the function?

 

[Sonal7]

Yes i got this one now. you just need to substitute t =1 to get to the answer in terms of e. The bit I was stuck on was what to do after you work out the G'(x), G''(x) . Once you get Var (X) in terms of those

Var (X)= G''(X)+G'(X)-(G'(X))^2 gives you the Variance but you have substitute the t as t=1. I dont quite know why but thats how to get the variance.

 

[nasi112]

If you can picture the question and upload it, I might be able to help you. Or at least, to write it completely as it is in the book.