Reply #66: [Add] up to 130%. How could that be? [View All]

[eomer]

Because you are mixing percentages that have different denominators. It is only when looking at a list of percentages that all have the same denominator that they will add up to 100%. (Edit: or, I should say, that they must add up to 100%. It is always possible that they may accidentally add up to 100%.)

For example, there is no reason that the percentage of U.S. residents who are male, plus the percentage of U.S. residents who are non-Hispanic should add up to 100%, right? The percentage who are male plus the percentage who are female should add to 100% and the percentage who are Hispanic plus the percentage who are non-Hispanic should add to 100% but the percentage who are male plus the percentage who are non-Hispanic will be something more than 100% (could be 130%). This last percentage is probably not useful for anything since we added two percentages that are unrelated to each other and therefore are not likely to end up with anything meaningful.

If you want to look at percentages with a denominator of total votes for Clinton or at percentages with a denominator of total votes for Obama, then using the same example would give these numbers:

Clinton Optical scan 10,000 25.00%
Clinton Hand-counted 30,000 75.00%

Obama Hand-counted 20,000 18.18%
Obama Optical scan 90,000 82.82%

They don't add up to 100% when combined with any of the percentages we were talking about before, because they are using a different denominator.