In this paper, a simple and obvious procedure is presented that allows to estimate π, the population proportion of a sensitive group, in addition to T, the probability that the respondents belonging to the sensitive group tell the truth whenever questioning directly. Properties of the estimators of π and T as well as sample size allocation are studied. And, efficiency comparisons are carried out to investigate the performance of the proposed method. It is found that the proposed strategy is more efficient than Warner's (1965) strategy, and has an additional advantage of deciding the optimal survey technique for practical situations.
