Hello,

I have two means (both of which are average antibody concentrations for a group of subjects calculated by multiplying all values and taking the nth root of this number, where n is the number of subjects with available data).

The first mean for group 1: 8985.

Group 1 is made up of 67 subjects.

The second mean for group 2: 7622

Group 2 is made up of 132 subjects.

I have been given the overall mean is 8056. However, I do not know how this number was arrived at. I have attempted the formula:

(67*8985)+(132*7622) = 1608099 / 67+132 = 8080.8995.

I don't understand where I am going wrong???