The population is all individuals aged 18 years or older in the State. A simple random sampling (SRS) method without stratification was used to select approximately 24,000 persons aged 18 years and over from the Census frame. With an SRS approach, every individual within the target population, who were aged 18 years and over, had an equal chance of selection regardless of demographics characteristics such as sex, age or self-perceived general health status. The Irish Health Survey has a weight variable to correct for non-response and sampling error. The weighting procedure had two steps: non-response adjustment and calibration. Design weights were calculated for all people in the initial sample. The design weights are computed as the inverse of the selection probability of the unit and were the same for all sampled due to the simple random sampling approach. The purpose of design weights is to eliminate the bias induced by unequal selection probabilities. Calibration of the non-response adjusted design weights then took place, calibrating to the population estimates at the level of sex, five-year age group, and NUTS 3 region using the Icarus-macro, developed by INSEE, for this purpose. To provide national population results, the survey results were weighted to represent the entire population.