In relation to its WVS surveys, the key aim of the WVS Association is to implement high quality standards in its methodology and to improve standards in the field of cross-national surveys more generally. Measuring values, norms, beliefs, and attitudes in cross-national perspective has challenges that go beyond those in national surveys conducted only in one country. For this reason, to generate the highest quality scientific data, Principal Investigators of the World Values Survey are required to observe the common principles and to follow the established rules.
Teams should avoid conducting survey in such and other times which reduce respondents’ availability and thus contribute to the sampling bias and higher non-response rate. In case any extraordinary events occurred during the WVS survey in the country, this should be documented in the survey technical report.
Unless the country’s territory is very big or planned sample size exceeds 3000 respondents, it is expected that the data collection shall be completed within 4 weeks’ time from the date of start of the first interview.
Sampling in WVS-8
WVS surveys are required to survey a national-wide representative sample of the adult population residing in the country. The sample must correspond to a set of established criteria. Sample should cover at least 95% of the country’s population. No country region should be deliberately excluded from the survey unless it is a remote location inhabited by 1-3% of the population. Alternatively, regions under military conflict where safety of interviewers and respondents cannot be guaranteed, can be excluded from the sample, following the recommendation of the local team.
Unless otherwise defined by the national legislature or by the existing established survey traditions, WVS samples should cover adult population in the age 18+. In exceptional cases (voting rights granted earlier; large share of young population) population in the age 16+ can be interviewed. No upper age limit for the respondent should be introduced in any country.
Unless the share of migrants exceeds 50%, WVS sample should cover residents and not only citizens. Category of “residents” does not include tourists or temporary visitors. In exceptional cases, countries with a large share of migrant population (i.e. UAE) can survey only nationals (whose share otherwise will be way too small for analysis, if surveyed proportionally to their share in the overall population). Migrant workers can be surveyed in case they have spent at least 24 months in the country prior to the survey date.
The exact approach must be further developed by every WVS national team. The ultimate goal is to cover all those population groups who comprise the structure of the country’s society at present (i.e. the sample must be representative in such a way that it reflects the main distributions observed in the country’s population by gender; age; urban/rural; education; income etc. groups). For this, the latest census or official statistical data (if census outdated) should be used to produce the sample calculations.
There are three main groups of countries in the WVS-8 depending on their sample size:
- the minimum acceptable sample size - i.e. the number of completed interviews which are included into the national data-set in vast majority of countries is 1200;
- for countries with the population of less than 2 million a sample size of 1000 respondents is acceptable;
- countries with bigger population and greater population distribution (Russia, China, Brazil, USA etc.) should aim at bigger sample size of minimum 1500 respondents.
WVSA relies on national team’s experience with regard to the optimal national sample size in a particular country.
Data collection modes in WVS-8
The main method of data collection in the WVS survey is face-to-face interview at respondent’s home / place of residence. Respondent’s answers could be recorded in a paper questionnaire (PAPI) or via CAPI (Computer Assisted Personal Interview).
Application of other methods of data collections (Internet panel, postal interview, telephone interview) is possible though requires justification by the survey team and assurance of the 95%+ population coverage. Possiblity of application of any alternative survey methods rather than PAPI and CAPI is considered on the country by country basis and requires approval of the WVSA Scientific Committee. Same requirements and procedure are valid for application of mixed mode surveys.