Critical Thinking - Understanding Correlation

No, this is not a statistics lesson, but here are a couple of examples to help better explain what is often falsely implied or misrepresented in the news.

Both articles happen to be about gum disease.  The first tells that the nearly-century-old belief that gum disease causes heart problems has been overturned.  “[T]here is no conclusive evidence that gum disease causes heart attacks and strokes, or that treating gum disease will improve heart disease…”  They don’t know yet why the two frequently occur together.  It could very well be that some unhealthy habits or lifestyle choices cause both.  When two events or conditions happen together, that’s not the end of the story.  The next step is to understand how and why A causes B or B causes A.  Perhaps they have a common cause.  Perhaps it’s just a statistical fluke.  In this case they admit that they don’t know why and are spreading the news in an attempt to correct the earlier erroneous conclusion.

The second article is about a correlation between obesity and gum disease.  Studies indicate that obese people have twice the likelihood of losing their teeth due to periodontal disease.  The fifth paragraph begins, “Why might this be? The researchers speculate…”  You see, the correlation does not mean causation.  They must find a link, explaining why they vary together and showing how one causes the other.  Until they do, it is unfair, possibly dishonest, to make a cause-effect connection.

So when the news media, a politician or an advertiser presents you with evidence that two things frequently occur at the same time or that they vary together, don't immediately buy the argument that the two are related.  Ask for more information.  How are they related?  What is the mechanism that makes one cause the other?  People trying to make their case often skip this step deeming it unnecessary, but they are wrong to do so.