The Environmental Health Barometer was modeled after the Health Barometers launched in 1992. It is therefore a repeated cross-sectional telephone survey based on a probability sample. This method involves initially selecting a finite number of individuals or households from a survey frame and sticking to this initial sample regardless of respondent acceptance (no replacements are made). This technique has the major advantage of increasing the probability of selecting individuals who are so difficult to reach that they are sometimes missed: in some cases, it takes more than twenty attempts to reach a household, which is accounted for in a random survey, whereas with the quota method, a household that cannot be reached on the first attempt may be quickly abandoned in favor of the next one on the list. The Computer-Assisted Telephone Interviewing (CATI) method used relies on an interactive system that improves the productivity of interviewers and team leaders in data collection. It relies on software that manages the organization of phone calls and dialing using a predictive system, scheduling appointments and rescheduling interviews when necessary, as well as the flow of the questionnaire (including filters and logic checks), the random rotation of question formats or items where applicable, and certain real-time checks on responses (inconsistent answers, reported impossible ages, etc.). In the case of the 2007 Health and Environment Barometer, the software used is Interviewer (Voxco Inc.). It allows for the monitoring at any time of indicators such as changes in refusal rates (overall or by interviewer), the average duration of the various questionnaire modules, etc.[chapter excerpt]