Tuesday, July 20, 2010

This Drives Me A Little Nuts

Here's a headline from yesterday's Wall Street Journal, article on page A2. The article discusses a study where, as you can see, a link was found between inner-city poverty and HIV.  If I were still teaching Six Sigma, I would use this as an example of the oh-so-common mistake of confusing correlation with causation.

Just because two things happen together (correlation) does not mean that one thing causes the other (causation).  There is often a third, hidden factor that causes both.  When I've taught this in the past, I stand  in front of the class and say something like, "High ice cream consumption causes sunburn."  Of course the class doesn't buy my argument, and we talk about how the hidden factors of sun and warm temperature likely cause both high ice cream consumption and sunburn.

So here we are on page 2 of the Wall Street Journal and I'm reading this article, getting more and more disturbed (relatively speaking) by the bad interpretation and reporting of this study.  In my opinionated little world, there's a third factor having something to do with impulse control or brain chemicals that may have something to do with both poverty and HIV.  To accent the thought, I was woken at 4:00 this morning by loud, music-playing neighbor-guest doing what his low impulse control has him do the best.  Get drunk, play loud music and yell, "God Bless America," and other things at the top of his lungs.  I resisted the impulse to call the police and moved to the sofa on the other side of the house to try and get that last 1-1/2 hours of sleep.


  1. Wow... low impulse control causes poverty? Yikes.

  2. Sarah - welcome to the blog. I am an engineer, not an expert on poverty and did not mean to imply anything at all about what causes poverty. I thought it was misleading for the Wall Street Journal to imply that poverty causes HIV, since that's not what I saw in the data they showed. That's all. I'm sorry you interpreted something different than I intended.