Hello, In the chapter 19 (Risk models 1) practice questions, question 19.4 requires you to recognise the probability function (below) as a type 2 negative binomial distribution. P(N=n) = 9(n+1)4^(-n-2) , n=0,1,2 the solution states that P(N=n)=(n+1 choose n)*(3/2)^2*(1/4)^n and hence deduces parameter values for k=2 and p=3/4. Please can you explain how one can recognise the above equation as a type 2 negative binomial and re-write in this way? Thanks in advance!
