Sample: nation-wide sample, 18-75
Sample size: n=500
Representative sample: in order to ensure a representative sample, telephone number selection considering landline and mobile phone user structure is used. Landline phone numbers are drawn from generally available phone registers.
Mobile phone numbers are generated basing on prefixes assigned to mobile operators within the Subscriber Number Usage in PLMN T2 Network. Numbers are generated in proportion to shares individual operators have in the market.
Such a number selection method guarantees a significant improvement in sample selection quality through minimizing of lack-of-coverage error (% of people not covered by the research).
Sampling: random-quota, up-to-date demographics from the Central Statistical Office are the basis for sample structure estimation. The Data includes:
- City size categories (5 categories: villages, cities: up to 50K, 50-200K, over 200K inhabitants, Warsaw). Sample stratification is done basing on this data in order to have all territories and city size categories in the sample strictly representing the distribution of Poles.
- Age (4 groups: 18-29, 30-44, 45-59, 60-75)
- Education (3 groups: elementary + basic vocational, secondary, higher)