On the occasion of my 5th blog-iversary recently, I listed my 10 most popular blog posts ever. To my surprise, my 9th most popular blog post ever was published just 2 months ago, which means it got strong immediate readership. It was my second take on what I have called “The Problem with Averages in Understanding Guns, Violence, and Crime.”
The heart of the problem is that averages, as summary statistics, can obscure significant underlying differences in the data producing the averages. Two very different distributions of data can result in the same average. Imagine a city that has two neighborhoods and a city-level average of 100 homicides per year. That average is the same whether those homicides are distributed evenly between the two neighborhoods or are concentrated entirely in one of the two neighborhoods. The average as a summary statistic only tells part of the story.
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