Self-administered online surveys may provide a higher level of privacy protection to respondents than surveys administered by an interviewer. Yet, studies indicate that asking sensitive questions is problematic also in self-administered surveys. Because respondents might not be willing to reveal the truth and provide answers that are subject to social desirability bias, the validity of prevalence estimates of sensitive behaviors from online surveys can be challenged. A well-known method to overcome these problems is the Randomized Response Technique (RRT). However, convincing evidence that the RRT provides more valid estimates than direct questioning in online surveys is still lacking. We therefore conducted an experimental study in which different implementations of the RRT, including two implementations of the so-called crosswise model, were tested and compared to direct questioning. Our study is an online survey (N = 6,037) on sensitive behaviors by students such as cheating in exams and plagiarism. Results vary considerably between different implementations, indicating that practical details have a strong effect on the performance of the RRT. Among all tested implementations, including direct questioning, the unrelated-question crosswise-model RRT yielded the highest estimates of student misconduct, which we would expect if the crosswise-model RRT is more valid than the other techniques. However, because the higher estimates may also be due to false positives, our results should not be taken as a proof for the superior validity of the crosswise-model RRT.
