Vigitel--Aracaju, Sergipe, 2008: the effects of post-stratification adjustments in correcting biases due to the small amount of households with a landline telephone.

INTRODUCTION

The Telephone Survey has several attractions, such as low operational costs and speed the process, when compared to the Household Survey. However, the exclusion of house holds without a landline phone canpose a serious question of the valid it yof the estimates.

OBJECTIVE

Evaluating the use of post stratification adjustments to correct the potential biasdue to low coverage of landline phonein the results published in the Vigitel system.

METHODS

We compared the prevalence obtained by the Household Survey and the Vigitel, in Aracaju, Sergipe, where 49% of households had a telephone, calculating the differences measured between the surveys thatused the square root mean square error as a measure of accuracy of the estimate.

RESULTS

The Household Survey showed ten variables associated with landline phone. From this set of variables, post stratification weights corrected the potential bias of the consumption of beans in five or more days per week, vegetables intake regularly and recommended self-assessment of health as bad and morbidity of diabetes,while the weights partially eliminated the bias of the prevalence of asthma, possession of health insurance coverage and prevention of breast cancer in women aged 50 to 59 years.

CONCLUSIONS

In order to reduce the potential bias in the results published by Vigitel system, in areas with low telephone coverage, it becomes necessary to use alternative weighting procedures and selection strategy of external variables for construction of post-stratification weights.