A validation of a computer-assisted randomized response survey to estimate the prevalence of fraud in social security

In the Netherlands, there is a research tradition that measures fraud against regulations by interviewing eligible individuals using a survey. In these studies the sensitive questions about fraud are posed by using a randomized response method. The paper describes the results of a Dutch study into the consequences of replacing home interviews by trained interviewers with Internet-delivered interviews in a survey on fraud in the area of disability benefits. Both surveys used computer-assisted self-interviews with randomized response questions. This study has three goals: first to present the research tradition that makes use of randomized response, second to compare the results of home interviews and the Internet survey and finally to introduce an adapted weighted logistic regression method to test the relationship between the probability of fraud and explanatory variables. The results show that there are no systematic differences between modes of interview, either for estimates of the prevalence of fraud or for the identification of associated variables. These outcomes result in the conclusion that the Internet survey is a useful and cost-effective instrument for measuring fraud in a population, and that it is unlikely that replacing home interviews with the Internet survey will result in a significant break with tradition. Copyright 2006 Royal Statistical Society.