I used to teach an IB maths course that had a lot of statistics in it. I used to enjoy looking for examples of bad uses of statistics in the media. Now it seems I’m finding them in my MS “journey”!
One of the most misused statistic is the average. When people hear average they typically mean the mean…the type of average where you add them all up and divide by how many you’ve got. Average age of the kids in a kindergarten class? Add up all the ages and divide by how many kids. 5.9 years old. Great. Average number of siblings each child has? Count all the siblings, divide by how many kids in the class. 2.3 siblings. Wait. No. How can you have 0.3 of a sibling?!?
There are three measures of the average of something. The mean, the mode and the median. If you don’t know what they are, well, hey, I’m not teaching anymore!!! If you need a refresher, watch this. In fact, if you don’t need a refresher, you should still watch it…
In an earlier post I mentioned the new drug that I’m about to take, Aubagio, a disease modifying drug that hopes to slow down the rate you have relapses. To recap: last year, my neurologist said he wouldn’t prescribe it, as its rate of reducing relapses was given in the research at just above 30% or so, the same rate as the drugs from 20 years ago. Why the change of heart, I asked? It seems that in practice what they’ve found out is the drug either works or it doesn’t – so it either reduces your rate by 0% or, I’m guessing, above 50% (my numbers, don’t quote me). It was simply incorrect to add them all up and divide by how many.
Today I read this article in the Guardian – Why doctors get it wrong about when you will die. Not the most thrilling title, and I opened it with some trepidation. However, once again it all comes down to statistics, or at least our understanding of statistics, and specifically averages. There’s also a great link in the article to the essay by Stephen Jay Gould about his response to being told he had 8 months to live.
What it comes down to is this: the next time your doctor tells what the average for something is, ask them what they mean, or mode, or median?!?