We’re not all statisticians but we are all, to some extent, programmed to reason statistically. In a bid to make sense of the world around us, we compare, contrast, look for patterns and are drawn to a statistical technique called correlation, a way of measuring the extent to which a change in one measurable thing – a ‘variable’ – is associated with the change in another measurable thing.
Indeed, you can calculate the correlation between pretty much any two things which can be quantified, counted and measured. But Statistics doesn’t operate as a set of techniques, its value is in providing insight into a problem, so if you are going to calculate correlations it makes sense for there to be some reason for doing it i.e. because you want to take action of some kind. SO there’s no point in looking for correlation between things which aren’t measurable such as eye colour and personality traits, or others which are clearly connected e.g. breast cancer and wearing skirts?. Or between entirely random things such as how many tatoos someone has and the amount of jam they eat each week. Any connection, mirroring or linearity found has to be down to chance. ’Findings’ here won’t tell you anything useful.
Despite this, tap correlation into your search engine and you’ll find many examples of the term correlation attached to nonsense association between all types of things, from ‘More surprising correlation’ to ’10 crazy correlations between unrelated things’ (the clue is in the title).
And worryingly… for some, it’s one short step from generating a graph, seeing a similar path between two things which happen at the same time or immediately after the other to begin thinking that one is responsible for the other i.e. that correlation implies causation. It doesn’t. Even when a relationship across time is identified, what correlation does not tell us is that one set of events (the effect) is a direct consequence of another (the cause).
An example of blindly leaping from correlation to causation? read the Daily Mail article ‘Drink more milk! you could win a Nobel prize’ - all about the ‘relationship’ between milk drinking and winning nobel prizes.
And yes, it’s all good fun (!) but there is a downside to it too. For some, it may suggest that there’s meaning and information in every kind of number pattern. There isn’t. It also taps into a widely-held fear that you can call numbers facts and make a case for anything. And that’s absolutely not what statistics is about.