As a scientist I know that correlation does not imply causation. Just because two things, A and B, are correlated does not imply that A causes B or vice versa. For example, there is a correlation between the number of pirates on the world’s oceans, and global temperature, but this does not imply that pirates, or their absence, is causing global warming. But even if there is cause and effect going on, then you still have to work out if A causes B, or if B causes A.
There is an article on the BBC website on the correlation between going to a private not state school, and going to a “top” university. The headline figures are that 46% of privately educated pupils but only 16% of state-school pupils go to these universities.
So OK, there is correlation here. Maybe there is cause and effect going on here too, or maybe not, but less us assume for the sake of argument that there is cause and effect here. In which direction is it working?
My impression is that the BBC article seems to be going along with the idea that a university being “top” causes it to have more privately educated students and fewer state educated pupils. However, “top” is defined here as having the highest A-level grade entrance requirements*. Private schools have greater resources than state schools and so coach their pupils more, presumably resulting in higher A-level grades. So, I wonder if cause-and-effect is working in the other direction. Those universities which are most popular with privately-educated pupils can ask for the highest grades and this causes them to become “top” universities.
I genuinely don’t know if there is cause and effect going on here, and if there is, in which direction it works. I don’t know if it is true that because a university is a top university, it attracts privately-educated pupils, or if because a university attracts privately educated pupils it is a top university. It could be a bit of both. The figures quoted above are government figures. If the government makes wrong assumptions about the direction of cause and effect here, and develops policy based on that assumption, the result could be a bit of a mess.
* Throughout this post I use “top university” to mean a university whose entrance grades are in the top third of all universities. In this I follow the BBC who follow the Department for Education. I think this is not a sensible definition, but that’s just my opinion.