Question 4: Assuming the data are correct, why are “r = –0.45” and “r = –0.22” obvious misprints on this graph?
The correlation coefficients for vocabulary should be positive, because older people have a larger vocabulary. The regression line slopes upwards.
Following a letter from Martin Bland, the following correction was printed in the Lancet, 18 March 2000: ‘. . . the correlation coefficients for vocabulary scores in the figure should be r = 0.45 for patients with mesial temporal-lobe epilepsy (MTLE) and r = 0.22 for controls . . .'.
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