Percentages not adding up I have a series of percentages:
132/220 (60%) and 88/220 (40%).
Now when I break them down into subcategories and then recalculate the percentages them come out 5% different.
81/140 (58%) and 59/140 (42%) (percentages ROUNDED).
21/40 (52.5%) and 19/40 (47.5%).
14/20 (70%) and  6/20 (30%).
16/20 (80%) and 4/20 (20%).
then we I do the averages I get:
65.125% and 34.875%
I have no idea what is happening???

If the samples/subcategories have different sizes, the average of the averages is not the same as the average of all numbers.
You have to make a weighted average: multiply each percentage by the size of the group, add them together and divide by the total size.
