Reader DE points me to this joke, given by Oxford professor Peter Donnelly in a 2006 TED talk:

Q: How do you tell the introverted statistician from an extroverted statistician?

A: The extroverted statistician is the one staring at the other person’s shoes.

I note however from his bio that Peter Donnelly is listed as a mathematician (despite his work in statistical genetics). I recall telling this same joke while I was working department shared by both mathematicians and statisticians, except the subject of the joke was mathematicians. Everyone has their stereotypes, I guess.

Despite the bad joke, the talk itself is well worth a look. It's an engaging look at common fallacies in statistics and probability, in particular the problem of inverting conditional probabilities (aka the Prosecutor's Fallacy). The example was one I hadn't heard of before, where Sally Clark, a mother in the UK, was convicted of murder after losing two children to cot death, and a paediatrician citied in expert testimony that the chances of this happening by accident was 1 in 73 million. Not only does this estimate assume independence of the two deaths, it's irrelevant: it tells us nothing about the relative likelihood of murder versus tragic accident. Sally Clark was later exonerated after two appeals, but adding further to the tragedy died suddenly in 2007.

On a lighter note, there was also an interesting stats puzzle I hadn't seen before. Imagine tossing a coin repeatedly until a certain sequence of three tosses is seen, say: HTH or HTT. On average, do you think it takes more or fewer tosses to see HTH or HTT, or is the expected count the same? Guess first, and then check the video below for the answer.

The impatient can skip ahead to 5:20 for the answer. (For the record, I guessed wrong.) This kind of problem has important applications in genetics. Finding a specific sequence of ACTG in a genome of millions of base-pairs is a harder problem than tossing coins, but the R package Biostrings solves it very efficiently.

When I first heard the joke (maybe a couple of decades ago now), it was directed at actuaries, but I've also heard it with "accountants", "statisticians" (a couple of times) and "mathematicians".

Posted by: GB | August 14, 2009 at 19:46

At this link you can see that the same joke is directed at computer scientists. We may infer that is a joke about introverted geeks.

Posted by: Paolo | August 15, 2009 at 00:19