 Noisy binary search can find the correct position of the target with a given probability that controls the reliability of the yielded position.Every noisy binary search procedure must make at least formula_171 comparisons on average, where formula_172 is the binary entropy function and formula_173 is the probability that the procedure yields the wrong position.The noisy binary search problem can be considered as a case of the Rényi-Ulam game, a variant of Twenty Questions where the answers may be wrong.