The ESS is characterized by scientific rigor and methodological sophistication. Three aspects are particularly important:
The source questionnaire must be developed very carefully in order to allow cross-country comparisons. The questions are pre-tested in several countries. Emphasis is placed also on the quality of question translations. The specialists of the ESS Core Scientific Team guide the national teams in their translation procedures. The specific practice for translation and assessment is called TRAPD (translation, review, adjudication, pretesting, and documentation).
Regional or international events can strongly affect attitudes and perceptions of survey participants. An act of terrorism or an economic crisis can have a strong impact on responses. Thus, the ESS records important media events during fieldwork (ESS media claims). This allows future data analysts a better understanding of the national contexts in which the questions were asked.
The quality of a survey depends in a high degree on the sample drawing procedures. The Core Scientific Team is supported by a group of specialists who advises and validates the national samples. In order to get a sample as representative as possible of the populations studied, the protocol forbids quota samples and encourages the participating countries to achieve high response rates. To this effect, the methodological procedures are constantly improved (e.g., intensive interviewer training). Since the third round, Switzerland has obtained a response rate of more than 50 percent, which is an exceptional result for the country. The interview is held face-to-face and lasts about one hour. Each interviewer conducts only a limited number of interviews in order to improve the quality of the raised data.
Summary table of the methodological features of the European Social Survey
- Target population: All individuals aged 15 and above who reside in Switzerland
- People surveyed: Random sample, with a minimum of 1,500 respondents
- Mode: Face-to-face interviews, CAPI
2002-2004: Random sampling in three stages:
- Sample of postal codes representing all regions of Switzerland
- Selection of a specified number of households from each of the sampled postal codes
- Random draw of one person within each household
2006-2008: Random sampling in two stages:
- Selection of a determinate number of households in every region of Switzerland (national register of phone numbers and addresses)
- Random draw of one person within each household/address
Since 2010: Random sampling in one stage:
- The ESS is declared a survey of national importance and funded by the Swiss National Science Foundation. Hence, a sample of individuals can be drawn randomly from the sampling register of the Swiss Federal Statistical Office, according to Art. 13c, para. 2, lett. d, order of 30th June 1993 regarding the implementation of federal statistical surveys.