Selection of NICOLA Participants
The method used to select participants for the NICOLA study was designed to ensure that the sample would be representative of the Northern Ireland population aged 50 years and over.
Over 400,000 adddresses were initially identified as having a household member aged 50 years or above. From these addresses, a smaller random sample, based on over 14,000 addresses, was selected to provide an overall representation of the Northern Ireland population.
Selected addresses were visited by an interviewer from Ipsos MORI (a market research company in Northern Ireland who were contracted by QUB to carry out the home interviews). All persons aged 50 years or over (and their spouses/partners of any age) were canvassed to participate in the survey.
A nationally representative sample of over 8,500 adults, aged 50 years and over and resident in Northern Ireland, were selected using this population sift.