Note that a PDF version of this detailled methodoloy is also availalbe
The major strategy of the ESPAD project is to standardise procedures as much as possible, including the target population, the questionnaire, the sampling procedure and the way in which data are collected. The 2015 ESPAD results are based on 35 national surveys using the common methodological guidelines presented in the ESPAD handbook.

This text provides an overview of different methodological aspects related to the 2015 data collections and ends with a short summary of the most important methodological findings to be taken into consideration in relation to the data quality. Apart from the results from the student questionnaire, information used in this text is based on the classroom reports filled in by the survey leaders and the standardised country reports provided by each national team. For discussions about ESPAD in relation to general survey methodology, please refer to the previous ESPAD report (Hibell et al., 2012).