I'm not sure if this is a excel question or a maths one.
I have three samples:
Population Number Rate Per 1000 Population
1000 150 150.000
2000 160 80.000
3000 170 56.667
In excel I've calculated the rate per 1000 by dividing the "number" by the "population" divided by 1000.
Anyway, I get the rates above. The problem comes with the average for the group. If I used Excel and average all three rate cells I get an overall average of 95.56.
HOWEVER if I sum the total "population" and the total "number" and divide using the same formula as above (i.e. dividing the "number" by the "population" divided by 1000) then I get 80.00
Is this Excel rounding numbers in the background? It all seems a bit wierd to me as they should be the same figure surely???
Many thanks
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