%0 Journal Article
%T Does sampling using random digit dialling really cost more than sampling from telephone directories: Debunking the myths
%A Baohui Yang
%A Margo Eyeson-Annan
%J BMC Medical Research Methodology
%D 2006
%I BioMed Central
%R 10.1186/1471-2288-6-6
%X This study compared an EWP sample and a LA-RDD sample from the New South Wales Population Health Survey in 2003 on demographic profiles, health estimates, coefficients of variation in weights, design effects on estimates, and cost effectiveness, on the basis of achieving the same level of precision of estimates.The LA-RDD sample better represented the population than the EWP sample, with a coefficient of variation of weights of 1.03 for LA-RDD compared with 1.21 for EWP, and average design effects of 2.00 for LA-RDD compared with 2.38 for EWP. Also, a LA-RDD sample can save up to 14.2% in cost compared to an EWP sample to achieve the same precision for health estimates.A LA-RDD sample better represents the population, which potentially leads to reduced bias in health estimates, and rather than costing more than EWP actually costs less.Computer assisted telephone interviewing (CATI) is widely used for health surveillance surveys. The main advantages of CATI over the traditional face-to-face interviewing are timeliness and substantial cost reduction to achieve the same sample size and geographical coverage via residential telephones. In Australia, there is little bias in population-based health estimates due to a high residential telephone coverage of 97.5%, [1] combined with post stratification weighting to the population.Even though full coverage of household telephones can be achieved by simple random digit dialling (RDD), it is not efficient due to inclusion of too many numbers that are not currently household telephone numbers (out-of-scope). The Waksberg Method improves the efficiency of RDD by using a two-stage sampling procedure, [2,3] and this method is widely used in studies outside Australia [4]. When relatively good quality lists of household telephones are available, and the list itself does not have satisfactory coverage of the target population, information in the list (such as prefixes) can be used to develop a sampling frame that has a better coverage
%U http://www.biomedcentral.com/1471-2288/6/6