Welsh Health Survey: Methodology

A random sample of addresses from the Postcode Address File is selected using a multi-stage probability sampling design with appropriate stratification. At each household all adults (those aged 16+) are eligible for inclusion in the survey. Data are collected continuously throughout the year.

The information is collected at two levels:

• Household - a short household interview with a responsible adult in the household.
• Individual - questionnaires to be completed and collected later:
  • From 2007 there are four individual questionnaires:
    • For adults aged 16+, a self-completion questionnaire
    • For children under 16, questionnaires (plus measurements of height and weight for those aged 2 and over) for three different age groups for a maximum of two randomly selected children in the household.
      0 - 3 year olds - questionnaire completed by a parent/guardian
      4 -12 year olds - questionnaire completed by a parent/guardian
      13-15 year olds - self-completion questionnaire
      
      
  • Prior to 2007 there were two individual questionnaires:
    • For adults aged 16+, a self-completion questionnaire
    • For children under 16, a short questionnaire completed by a parent/guardian for all children in the household.

An achieved sample of around 15,000 adults and 3,500 children is aimed for per year, to include a minimum 600 adults from each local authority area. The effective sample sizes will be somewhat smaller because of design effects (the survey involves a clustered design).

The survey is conducted by the National Centre for Social Research (NatCen) on behalf of the Welsh Assembly.