Archive for September 6, 2017

More Worthless University Rankings

Posted in Bad Statistics, Education with tags , , , on September 6, 2017 by telescoper

The Times Higher World University Rankings, which were released this week. The main table can be found here and the methodology used to concoct them here.

Here I wish to reiterate the objection I made last year and the year before that to the way these tables are manipulated year on year to create an artificial “churn” that renders them unreliable and impossible to interpret in any objective way. In other words, they’re worthless. This year the narrative text includes:

This year’s list of the best universities in the world is led by two UK universities for the first time. The University of Oxford has held on to the number one spot for the second year in a row, while the University of Cambridge has jumped from fourth to second place.

Overall, European institutions occupy half of the top 200 places, with the Netherlands and Germany joining the UK as the most-represented countries. Italy, Spain and the Netherlands each have new number ones.

Another notable trend is the continued rise of China. The Asian giant is now home to two universities in the top 30: Peking and Tsinghua. The Beijing duo now outrank several prestigious institutions in Europe and the US. Meanwhile, almost all Chinese universities have improved, signalling that the country’s commitments to investment has bolstered results year-on-year.

In contrast, two-fifths of the US institutions in the top 200 (29 out of 62) have dropped places. In total, 77 countries feature in the table.

These comments are all predicated on the assumption that any changes since the last tables represent changes in data (which in turn are assumed to be relevant to how good a university is) rather than changes in the methodology used to analyse that data. Unfortunately, every single year the Times Higher changes its methodology. This time we are told:

This year, we have made a slight improvement to how we handle our papers per academic staff calculation, and expanded the number of broad subject areas that we use.

What has been the effect of these changes? We are not told. The question that must be asked is how can we be sure that any change in league table position for an institution from year to year represents a change in “performance”,rather than a change in the way metrics are constructed and/or combined? Would you trust the outcome of a medical trial in which the response of two groups of patients (e.g. one given medication and the other placebo) were assessed with two different measurement techniques?

There is an obvious and easy way to test for the size of this effect, which is to construct a parallel set of league tables, with this year’s input data but last year’s methodology, which would make it easy to isolate changes in methodology from changes in the performance indicators. The Times Higher – along with other purveyors of similar statistical twaddle – refuses to do this. No scientifically literate person would accept the result of this kind of study unless the systematic effects can be shown to be under control. There is a very easy way for the Times Higher to address this question: all they need to do is publish a set of league tables using, say, the 2016/17 methodology and the 2017/18 data, for comparison with those constructed using this year’s methodology on the 2017/18 data. Any differences between these two tables will give a clear indication of the reliability (or otherwise) of the rankings.

I challenged the Times Higher to do this last year, and they refused. You can draw your own conclusions about why.

P.S. For the record, Cardiff University is 162nd in this year’s table, a rise of 20 places on last year. My former institution, the University of Sussex, is up two places to joint 147th. Whether these changes are anything other than artifacts of the data analysis I very much doubt.