Far better an approximate answer to the right question, which is often vague, than an exact answer to the wrong question, which can always be made precise.

John Tukey (1915-2000) American mathematician and statistician

“The future of data analysis,” Annals of Mathematical Statistics 33 (1) (1962)

Paraphrased in Super Freakonomics as: "An approximate answer to the right question is worth a great deal more than a precise answer to the wrong question."