Int. J. Environ. Res. Public Health 2009, 6 698 some terms, identify the items to be retained as well as the sensitive issues to be excluded; 3) development of an initial version of the questionnaire; 4) conducting telephone interviews with 61 people aged 18 years or older (on average, four people per health region studied) to validate the clarity and precision of the questions, to comment on the questionnaire and to shorten it; 5) validation of the content of the questionnaire (French and English versions) by five experts working in the field of health and climate change in Canada; 6) conducting of a qualitative pretest (n=50) (two versions of the questionnaire) by the polling firm, at the start of each data collection. 2.3. Analyses The collected information was calibration weighted for the respondent’s age and language, on the basis of 2001 census data [21]. Coefficients of variation (CV) – or relative standard deviation [22] – were calculated (CV < 15%: sufficiently precise estimates; CV between 15% and 25%: acceptable precision, estimates to be carefully interpreted; CV>25%: low precision, estimates to be interpreted with circumspection) [23]. The percentages totals for a given variable may not be exactly 100%, due to rounding to the closest decimal (to simplify the presentation, percentages below 2% for missing data have not been reported). The analyses took into account the sample scheme stratified according to the health regions [24,25]. Using a remote car starter in winter was related to the independent variables with the help of the Rao-Scott likelihood ratio chi-square test, which is a design-adjusted version of the Pearson chi-square test. The multivariate analyses were done using a logistic regression model with a stepwise method (significance level required to include in the model: 0.2; to stay in the model: 0.1). The c index (area under the ROC curve; expected value = 0.5 to 1.0) was used as an indicator of the discriminant capacity of the final multivariate statistical model [26]. Finally, the presence of collinearity between the independent variables was checked (VIF > 10; condition > 30) [27]. 3. Results 3.1. Characteristics of the Respondents Women accounted for slightly more than half of the sample, as well as did people 35 to 64 years of age (Table 2). At least two participants out of three lived in a house and spoke only French (Table 2), except in Montréal and Laval (Table 3). More than half of the respondents (56.8%) used a car every day, and 27.0%, less than once a day (never: 16.2%). In the first group, 32.9% used a remote car starter in winter and in the second group, 27.4%. 3.2. Factors Associated with the Use of a Remote Car Starter in Winter The prevalence of use of a remote car starter in winter was higher for women than for men, as well as for francophones, or people with a mother tongue other than English or French (called allophones in Canada), compared to anglophones (Table 4). Higher percentages of respondents using a remote car starter at least occasionally during the winter were observed for those individuals living in a house, in particular in the peripheral regions of southern Québec than in the more urban environments (Table 4),