ESPAD 2019 Methodology

Since its inception, the major objective of ESPAD has been to create a cross-sectional survey that, taking account of the specificities of the national contexts, uses a common methodology in order to make the data comparable between countries and across years. This mainly means basing the implementation of the survey in each country on standardised procedures, including with regard to the target population, the questionnaire, the sampling procedure, the way in which data are collected and data cleaning methods of national databases (e.g. missing values, imputation). The common methodological guidelines for each survey wave are provided in the ESPAD handbook for all participating countries. Besides providing an overview of different methodological aspects related to the data collection, the ESPAD methodology reports, produced to describe the 2015 and 2019 data collections, end with a short summary of the most important methodological considerations in relation to the data quality in each country. Therefore, the 2019 survey wave took into account and tried to address the methodological challenges faced by each country in the 2015 data collection (ESPAD Group, 2016b) in order to increase the quality of the study. The information provided in this text is based on the results of the student questionnaire, classroom reports filled in by the survey leaders and the standardised country reports provided by each national team.