FWIW, the exact quote (from pp.13-14 of this article) is:

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

Your paraphrase is snappier though (as well as being less ambiguous; it's hard to tell in the original whether Tukey intends the adjectives "vague" and "precise" to apply to the questions or the answers).