11-24, 13:40–13:55 (Australia/Melbourne), Zoom Breakout Room 3
The Integrated Public Number Database (IPND) provides access to all Australian mobile telephone numbers. Unlike random digit dialling (RDD), the IPND also provides the postcode at which the number is registered. The availability of postcodes is critical for affordable research at the state level and below because Australian mobile numbering is not related to geography. As a result of the cost of screening for sub-national samples, contemporary Australian telephone surveys typically use a blend of mobile RDD and listed mobile sample for cost control. (Landline RDD has largely been discontinued due to declining coverage, increasing coverage error and increasing cost.) Although the IPND has been available for some time for a limited set of use-cases (public health research, Commonwealth public policy research and party political research for candidates or parties), there has been no systematic investigation into the quality and efficiency of the IPND relative to RDD; an absence that this paper aims to remedy. We describe the results of (1) a systematic trial conducted on the IPND by the Social Research Centre, in partnership with various state and territory health agencies and Cancer Council Victoria (CCV) and (2) parallel administration of RDD and IPND in the CCV’s 2022 Victorian Smoking and Health Survey.
We first present a brief overview of the IPND and its limitations. The accuracy of geographic information from the IPND trial is shown, at levels from state (correct in 93% of cases) to postcode (correct in 75% of cases) and it is demonstrated that no appreciable coverage error was identified. The results of RDD and IPND samples on demographics and selected health outcomes and behavioural measures are compared. With the possible exception of the proportion of very young adults (i.e. 18-19 year-olds) responding, both unweighted achieved sample and weighted estimates are consistent between RDD and IPND.
The results of this paper show that the IPND is fit-for-purpose for public health research that has to date used RDD-based designs. Compared to a hypothetical single frame mobile RDD design for a state-level survey, IPND will yield similar estimates and sample characteristics but at reduced cost, due to reduced need for screening. Compared to the dual-frame mobile RDD and listed designs that are actually in use, costs should be broadly similar but the IPND is preferable because it offers the benefits of a pure probability design and higher weighting efficiency compared to the dual-frame alternative.
Dr Benjamin Phillips is Chief Survey Methodologist at the Social Research Centre and has over 17 years of experience in social research. He develops and applies survey methodology for Social Research Centre projects, including Life in Australia™, Australia’s only probability online panel, the Quality Indicators for Learning and Teaching [QILT] suite of surveys for the Australian Government Department of Education, Skills and Employment, the Monash University/Scanlon Foundation Mapping Social Cohesion Survey and the Lowy Institute Poll.