How to compare with one number?

From: davegb (davegb_at_safebrowse.com)
Date: 03/21/05 

Date: 21 Mar 2005 08:50:15 -0800

I'm definitely not a statistician, so I'm looking for some help. If
I've posted to the wrong group, please re-direct me to the correct NG.
I am working for the state Child Welfare Dpt., doing some moderately
sophisticated Excel spread*** for them. I've been asked to create a
comparator to give them one number to rank the 64 counties in certain
state and federal mandated areas. I'm sure I'm not the first person to
have this need.
In each of the 64 counties, we measure how many clients we have total,
how many had a certain event occur while they were our clients. We post
these numbers in a spread***, along with the percentage of occurences
within each county and percentage that occured in county compared to
the total clients in state. The problem it this. In the large counties
(population wise), we have statistically significant numbers of clients
(100's or even 1000's) so the percentage of occurences is relevant. In
some of the smaller counties, we may have as few as 3 or 4 clients
(actually, some have zero, but they're not the problem). If there is an
event occurence with 1 client out of 4, that's 25% of the county client
population, and extremely large number in this dataset. It looks bad in
the state percentage column until you look at total number of clients
in that county.
I'm looking for a way to create an additional column on the spread***
with one number that takes into account the total number of clients,
and reflects the fact that even thought the percentage might be high,
the sampling is too small to be revelant.
One thing that's occured to me is to create a formula that sets a
minimum number of clients, and if it is below that minimum, shows a
test message saying something to the effect of "Sampling not relevant".
But if there's a statistically better way of doing this, I'd like to
use it.
Thanks for your help. If my explanation is unclear, please ask for more
information so you can suggest ideas.

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