Monday, May 12, 2014

Spurious Correlations

Orac alerted me to a web site that is simply wonderful. You know when you hear someone talk about the increase in the number of shots on the vaccination schedule and how it correlates to the increase in autism diagnoses in the U.S.? Send them to Things that Correlate (aka Spurious Correlations). This is an amazing site that provides all sorts of graphs showing how two completely unrelated things appear to correlate. For example, did you know that the fewer lawyers there are in the Northern Mariana Islands, the lower the divorce rate in Kentucky? It's true:

Credit: tylervigen.com
Clearly there's something going on here. There has to be a connection. I mean, how else do you explain how closely those lines match up? It can't just be coincidence. Or at least, no more coincidence than the number of vaccines on the recommended childhood schedule and autism. I guess if we want to keep couples together in Kentucky, we need to make sure that there are as few lawyers in the Northern Mariana Islands as possible. I mean, the data's right there.

This should, hopefully, illustrate how just because two things appear to be correlated, does not mean they really are, nor that there is any sort of causal connection between the two. You can even look for your own correlations by clicking on the "Discover a new correlation" link. Just pick your starting category, then your first variable and finally your second variable. You can see how close is the correlation by looking at the number in parentheses. The closer to 1, the closer the correlation. The closer to -1, the closer to an inverse correlation. Then just click on "Correlate" to see your graph.

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