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My data is grouped into 42 categories according to classification of bird catch. Each group contains "X" amount of species, but for ease of input we categorize them into subsets. For example:

Group 1: 265.5 kg

Group 2: 47 kg

Group 3: 213.5 kg

etc....

Group 42: 63 kg

The sum is equal to 4765 kg. However, to get the average, the total is divided by 400 which is the total amount of birds per people catching them. Hence, the average catch per person is roughly 12 birds. Now if I take the std. deviation of the groups' averages (4765 kg) I get 92.6. Dividing that by 400 I get 0.23 kg.

My question is this; can I simply take the standard deviation of the 'population' whole (each group's average) and divide it by 400? Or is it much more complex due to squaring. Do I need to collate the entire data set into weight of individual birds (not groups)? If I take the std. deviation of every individual birds weight, the result is 3.19 kg. However, this is for every bird

**not birds/person.**

Regards,