You are a star!
One additional important fact has been donated by my statistically literate daughter who showed me the text book data on representative sampling. The key is that for target population sizes in excess of 10,000 and a scientifically acceptable margin if error of 5% the sample size needs to be 370 minimum.
I now have the crucial data that I need for next month's RAeS Conference talk.
Thanks to all.
G.
