for each assessment lasting approximately two to three hours). Multiple telephone contacts (including scripted messages for telephone answering machines) were made to each number, and letters describing the study were sent to addresses (when available) of households that hung up or initially refused to identify whether a child of the eligible age range was present. Recruitment began in April 2007 and was completed in February 2009. The participation rate for those completing the interview was 52.4% (387/739), which is well within the range of population-based studies (Galea & Tracy, 2007).
