Extreme measures

Aditya Chakrabortty (Brain food, G2, 4 January) is probably right that many drivers overestimate their ability, but he is wrong to claim that 95% being above average is a mathematical impossibility. To keep the numbers simple, suppose that driving ability is rated on a scale from 0 to 20, and out of every 20 drivers, 19 score 20 and 1 scores 0. The average score is then 19, and 95% of drivers do better. It's quite likely that well over 50% of drivers are of above average ability, since most drivers are moderately competent, few are really good, but a significant minority should never have been allowed on the road. That minority drags the average down, leaving everybody else above it. The 50% break-even point is the median, and this is often a better measure of typical behaviour.

Ian Stewart

University of Warwick

• Norman Druker (Letters, 6 January) cites Ginger Baker's song T.U.S.A. regarding making the perfect cup of tea, but instructions set to music could not be clearer than Django Bates' gem of a song The Importance of Boiling Water, on the album called Like Life – diffusion music at its best. However, I think criticism of the US to be a little misplaced since it's almost impossible to get a decent cup of tea anywhere, particularly in London.

Robert Brady

Twickenham, Middlesex

• "Soon be available here"? (Make mine a schooner…, G2, 6 January). We were drinking draught sherry from schooners in Berni Inns back in the 60s.

Mike Broadbent


• I note in the Education Guardian (4 January) a University of Leeds job advert for a "director of exploitation and commercialisation". How appropriate in the current climate, only confirming that the market will rule HE if current proposals are allowed to go through and the public value of HE is lost for ever.

Jol Miskin


• Eric Cole (Letters, 6 January) asks how many Waleses there would be in the area under flood in Australia, "the size of France and Germany combined" (Report, 3 January). About 44 – or around 1.1 New South Waleses.

Scott Poynting


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