When this came through my inbox this morning, all I could think was, “How have I never found this blog before?” Harvard Business Review has a new article – “Beware Spurious Correlations” – that features the absurd (like an example of how iPhone sales correlates visually with U.S. deaths from falling down stairs) and the serious implications of what that means for those visualizing data and inferring unproven causal relationships.
The teaser from HBR:
“We all know the truism “Correlation doesn’t imply causation,” but when we see lines sloping together, bars rising together, or points on a scatterplot clustering, the data practically begs us to assign a reason. We want to believe one exists.
Statistically we can’t make that leap, however. Charts that show a close correlation are often relying on a visual parlor trick to imply a relationship. Tyler Vigen, a JD student at Harvard Law School and the author of Spurious Correlations, has made sport of this on his website, which charts farcical correlations—for example, between U.S. per capita margarine consumption and the divorce rate in Maine.”
Read the article for the full explanation, but all to say, be thoughtful about how you visualize your data – don’t fall prey to misleading with charts and graphs.