Sunday, November 22, 2015

On Statistics, Reporting and Bacon

I've previously ranted about the need for a "journalistic analytics" college major, to help with reporting (and editing) news containing statistical analysis. Today I read an otherwise well written article that inadvertently demonstrates how easy it is for even seasoned reporters to slip up.

The cover story of the November 9 issue of Time magazine, written by Jeffrey Kluger, has the title "Red Meat, Hot Dogs and the War on Delicious". It's main focus is a recent meta-analysis that found links between consumption of meat (and particularly processed meat) and colorectal cancer. As a Time subscriber, I've read quite a few articles by Mr. Kluger, who covers the "science beat" for them, and I have a great deal of respect for his ability to interpret scientific evidence and present it both accurately and interestingly. So I was a bit bemused to encounter the following paragraph (approximately midway through the article):
Figures like that are not always easy to understand and can be more alarming than they need to be. The lifetime risk for developing colorectal cancer is just 5% for men and a little lower for women. A hot dog a day would raise that risk by 18% of the 5%–topping you out at about a 6% overall risk. But that assumes that’s all the red meat you ever eat, and those 1% increments add up fast.
Unless the lifetime risk statistics are for confirmed vegetarians (which I doubt), the rise from 5% to 6% lifetime risk would be caused by one hot dog a day (or equivalent) added to your normal diet. Presuming the morbidity statistics were for US citizens (the core audience for Time, I assume), we can put this in the context of a statistic from an earlier paragraph:
In 2013, the average American consumed more than 71 lb. of beef, lamb, veal and pork ...
I'm pretty sure that 71 lb. per person excludes "turkey bacon" and possibly a few other meats that, while not technically "red meats", were found to contain the same nitrates and nitrites that were associated with cancer risk in the meta-study. So the "normal diet" to which you're adding that incremental hot dog per day (or equivalent, for those of you who don't really want an extra hot dog every day) is not exactly devoid of meat products. Therefore, "[b]ut that assumes that's all the read meat you ever eat" is incorrect. (According to my scale, "those 1% increments add up fast" is indeed accurate.)

I don't want to belabor this, nor to find fault with Mr. Kluger (or his editor and/or fact-checker). It's just evidence that even seasoned reporters can commit an occasional statistical faux pas when the flow of the narrative grips them.

low carb and gluten free salad (bacon)