Correlation and Causation

Another favorite of misusers of statistics is the old: if A follows B, B must have caused A. So take as a piece of statistical evidence that the poor do worse on IQ tests (or SATs) than the rich. Well, this means that the poor aren't as smart, and their lack of intelligence is causing their poverty, right? Nonsense. It could as easily be (and is) the case that the tests are written by the relatively wealthy for the relatively wealthy, and as a result the wealthy understand the assumptions and so on and do better. Statistics certainly can't make that decision-- to figure out causation of a thing like this, we have to look carefully at the evidence.

You can find correlations (meaning as one thing goes up, another does (for positive correlation) , or as X goes up Y goes down (for negative correlation) ) between all kinds of things: The price of rice in India has a strong correlation to teachers' salaries in Quebec. Does this mean that one is causing the other? (Or is inflation responsible for both?)



Next         Prev         Home