Re: A statistical list problem

christof@xxxxxxxxx wrote in news:1157030889.770379.78350
@m79g2000cwm.googlegroups.com:

I have a list of n elements. I've marked m elements in the list
(1<=m<=n). Now I want to search to the list until I found an UNMARKED
element. How many elements do I have to search through in average?
For m=1 the answer is probably: 1 + 1/n
For m=2: 1 + 2/n + 2/n * 1/(n-1)
I call this the function f(m)

My question now is: How many elements do I have to search through for
the summary of all possible m values. That means:

f(1) + f(2) + ... + f(n) = ???


Can somebody help me with the problem?


Try searching on the term "negative binomial". The mean of a NB(k;r,p)
distribution is r(1-p)/p

--
David Winsemius.
.