Numerical drift

I see from your report (3 December) that Scotland scores a higher mark than England in the PISA assessment on mathematics.

What is more intriguing is that both countries, with marks of 498 and 495, exceed the UK figure of 494.

I hope that Wales and Northern Ireland do not provide the dead weight to drag the average down. I would guess, however, that the old escape clause of “rounding error” will provide the explanation.

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If so, it suggests that some statistics are ill fitted to bear the interpretations put on them. Maybe they have caught the current ailment affecting numbers in wider debates.

LV McEwan