The method used to select participants for the TILDA study was designed to ensure that the sample would be representative of the Irish population aged 50 and over. An initial multi-stage sample of addresses was chosen by means of the RANSAM sampling procedure, which was developed by the Economic and Social Research Institute (ESRI) based on the Irish Geodirectory, a comprehensive and up-to-date listing and mapping of residential addresses in Ireland compiled by the Ordinance Survey Office. Each address in the country has an equal probability of selection from the sample list of addresses.
A nationally representative sample of at least 8,000 adults aged 50 and over, resident in Ireland, was selected using a population sift. The selected addresses were visited by an interviewer from Ipsos MORI and all persons aged 50 or over (and their spouses/partners of any age) were canvassed to participate in the survey. 8,504 participants were recruited to the study. These include 8,175 respondents aged 50+ and 329 younger partners of eligible individuals. The household response rate to the study was 62%.