In most countries, the survey involved national population samples, but others were done only in urban areas.
The population sample was aged between 15 and 24.
The population sample consisted of the respondents being 30% female and 70% male.
The population sample was the largest ever for this kind of study, as was its timescale (twenty-five years from 1960 to 1985).
Some measurements are selected, and are applied to a population sample.
The prevalence in the population sample is calculated to be:
Many of them are closely related to the parameters found in statistics for characterizing population samples.
This study was based on a population sample of family physicians and rheumatologists.
Doing that European Union-wide means a larger population sample and more useful data.
No other country has ever IQ tested a total population sample in this way.