June 6, 2020

Looking clueless

I saw this ‘infographic’ on the Twitter feed of a civil rights lawyer in the US

The implication is so obviously wrong that you’d wonder how someone would fail to notice: 58% is about three times 19%, not seven times.  I wondered if this was a confusion of rate ratios and odds ratios, but that didn’t explain it either. So I went to the New York Times story, and saw this at the top of the page

Same numbers in the graph: a three-fold difference. Almost the same claim in the text —  a seven-fold difference — but now with a reference group.

If you read carefully, they are both right.  The graph (and all the graphs in the story) compare Blacks (20% of the populaton) to non-Blacks (80%).  The headline compares Black and white (60%), and the relative rate there is a bit above seven.  To find the numbers for this comparison, you just need to read the sections highlighted in red here

That’s three separate paragraphs, with a map in the middle.

Both the graph and the headline are very suited to social media (‘clickbait’ is a bit strong, since it’s actually good data). They will be circulated by lots of progressive US people who, like the lawyer whose tweet I first noticed, will look numerically clueless.   That can’t be good for the Times.

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Comments

  • avatar
    Steve Curtis

    Another point remember is the City of Minneapolis with its own police force is 430,000 people. The metropolitan area is much bigger with 3.5 mill divided into many other municipalities often with their own police force. Police operate within their own area while residents move freely for work, socialising entertainment etc. Its not a surprise a large number of force incidents happen in the major downtown area, which is within Minneapolis City.

    4 years ago