03 July 2008

Bad math (sort of)


Consider the graphic on the left from the AP. The key here is the text associated with the graphic: "The percentage of Americans now using broadband to connect to the Internet has increased 52 percent since 2000."

The wording is a little strange. Yes, the percentage has increased 52 percent, and strictly speaking, that is correct. But is that really what they're trying to demonstrate? It's only my guess, but I don't think so.

Now, consider how they arrived at that number. In 2000, 3% used broadband. In 2008, 55% use broadband. So 55%-3%=52%. Right. But it's not a 52% increase.

Let's assume our entire sample is 100 people. If three people used broadband, and in the next year six people used broadband, this is twice as many people--or a 100% increase. In fact, using 2000 as the baseline, every increase of three people (or 3%) is equivalent to a 100% increase in broadband usage. So it's clear that the math in this AP graphic is poorly represented. While technically correct, the number itself provides no real useful information because 52% doesn't really mean anything.

The method to find the correct answer to this graphic is represented by: "55 is what percentage of 3?" The answer is 1833.3% which makes sense if every three percent is a 100% increase. 55/3=18.3.
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