Bringing these experts together to discuss their suggested revisions in a group setting can be very beneficial in terms of developing consensus on the surveys content and approach to measurement. Cognitive tests thus provide a measure of the reliability and validity of questions and can help identify potential sources of measurement error. Cognitive testing can also help identify whether other aspects of the survey, such as the time required to complete the interview and safety measures that have been put in place, are feasible and acceptable to respondents. Typically, cognitive testing occurs in a laboratory setting with specially trained cognitive interviewers testing a small pool of participants, the number of participants can, however, be expanded according to available resources (UNODC and UNECE, 2010).