I look around my classroom, currently devoted to the S2 statistics module. Brows are knitted as we tackle the topic of correlation. An exam question is on the board and we have reached a crucial point in choosing our strategy; we are mathematical surgeons, about to pick the best scalpel.
“So what do we need here?” I ask, hopefully. Looking innocent, Graham puts up his hand. “Is it Superman’s rank correlation coefficient?” he asks. And suddenly, in my mind’s eye, I am in Metropolis ...
Walters, Evans and Simcock, the three grey-suited men around the table, look at each other. The nucleus of the National Security Statistics Board, they are talking in tense whispers; the seriousness of their discussion is obvious to the most casual observer. On a projector screen is a scatter diagram, with 30 points arranged on it. The variables are so secret that no one has been permitted to label them on the diagram.
“It’s no good,” whispers Walters. “We can’t use the PMCC for this test.”
“No,” agrees Evans. “We have to have a bivariate normal distribution for that to work and, well...”
“The evidence for that would be an elliptical arrangement of dots,” chips in Simcock. “And we hardly have that. There does appear to be some association...”
“But it won’t be linear, will it?” says Walters, ashen-faced. “And if we can’t complete this test...” His voice tails off.
“It’s the end of civilisation as we know it,” says Evans, grimly.
“Wait!” says Simcock, suddenly spotting something out of the window. “Is that a bird? Or is it a plane?”
“Gentlemen, I know what that is!” cries Walters. “It’s not a bird, it’s not a plane, it’s a rank correlation coefficient! We are saved! We’d better open the window.”
A few moments later, Superman dusts himself down. “Mr Spearman sends his apologies,” he says. “He can’t be here in person, but I’ve brought his non-parametric test along. Just what you need, I think.”
“And just in the nick of time, Superman!” cries Evans.
I snap out of my reverie to see a concerned-looking set of pupils gazing at me. “Er...it’s Spearman’s, not Superman’s, Graham, I think you’ll find,” I say, quickly.
We all love superheroes, so why can’t we have a mathematical one, indeed a whole stable of them? It is true that the greats of the past like Archimedes, Gauss and Euler have superhero status in maths teachers’ minds, but their accomplishments are harder for our proteges to appreciate.
The decoding stars at Bletchley Park (who, according to some, shortened the war by two years) are perhaps more likely pin-ups, but is it not always the mythical heroes who capture our imaginations the most?
So what’s it going to be for my next lesson? Batgirl’s minimum connector algorithm or Spider-Man’s remainder theorem?
Jonny Griffiths teaches maths at a sixth-form college
What else?
Jonny Griffiths’ collection of resources will help you to conquer the S2 statistics module. bit.lytesStatistics
Try Astronyxis’ lesson on Spearman’s rank correlation coefficient. bit.lytesSpearman.
