Sir – Oxford is ‘Extremely unaffordable’? The article on April 16 highlights yet again the problem of averages.

At a time of relative financial meltdown understanding averages becomes crucial to any survival of optimism.

It is quite simple really — there are three standard ways of calculating an average — the mean, the mode and the median. Any standard textbook will explain how to calculate these.

If you want to frighten people about house prices you calculate an arithmetic mean.

If you want to reassure people you present a mode and a median as well.

Or you can calculate an arithmetic mean which includes information on distribution.

There really are fewer houses in Oxford selling at more than a £1m than there are houses selling at £250,000 or less.

Your article rightly hinted at this in the sub headline ‘For every £3m Norham Gardens Mansion there is some flat or house for £175,000’.

Of course we know why the press prefers the arithmetic mean — it is much more frightening and much more exaggerated!

Mary Hodges, Oxford