Validade de estimativas obtidas por inquérito telefônico: comparação entre VIGITEL 2008 e Inquérito Saúde em Beagá Validity of data collected by telephone survey: a comparison of Vigitel 2008 and 'Saúde em Beagá' survey

Abstract Objective : To assess the validity of the estimates obtained through telephone survey and to measure the impact of the post-stratification weighting factor to adjust estimates. Methods : The same questionnaire was completed by two independent samples of the population living in the municipal-ity of Belo Horizonte city (Barreiro and West regions). One sample (n=440) completed the questionnaire of VIGITEL 2008 (telephone survey), and the other (n=4,048) of Saude em Beaga (face to face household interview). The results of the two samples for 18 health-related variables were compared by means of test statistics. At first, residents who had a landline telephone line were compared to those who reported not having a telephone line; then, VIGITEL estimates, with and without post-stratification weight, were compared with Saude em Beaga estimates. Results : Subjects who owned a landline telephone line had indicators for better economic conditions (housing, schooling, and skin color); higher prevalence of chronic diseases; lower exposure to risk factors for chronic diseases; and improved access to health services, compared to the those who reported not having a telephone line. Most VIGITEL estimates (without post-stratifi-cation weight) were similar to the sample of