The randomized response method was developed by S. L. Warner in 1965 to provide survey participants with a particularly convincing guarantee of the anonymity of their information and to encourage them to give truthful answers to questions on sensitive topics. This involves randomly dividing respondents into two groups, only one of which is instructed to answer a yes/no question on a socially undesirable behavior truthfully, while the members of the other group are asked to answer yes to the question regardless of their actual behavior. In surveys on the prevalence of doping among German top athletes (cf. module on Studies on doping among German top athletes), scientists around Werner Pitsch instructed the participants, for example, to only give an honest answer to the question of whether they had ever taken banned doping substances for the purpose of improving performance if their mother's birthday was between May and December. If, on the other hand, she was born between January and April, the participants should answer the question positively in any case. As the scientists had no information on the birthdays of the survey participants' mothers, they could not determine for any individual participant whether a positive answer to the question indicated that he or she had actually taken doping substances before. However, because the relative frequency of births in the months January to April is known, it is possible to determine the proportion of respondents who answered "yes" to the question of interest.