Policy-centred sampling in interest group research: Lessons from the INTEREURO project

Proper sampling is the foundation for all scientific enquiry aimed at making generalizable claims about a wider set of cases. Indeed, inferential statistical analysis presupposes representative samples and units of analysis that can be considered as independent observations. Establishing a sample of issues on which lobbying may take place, which is at the same time representative of an overall population of issues and of the varying levels of conflict and political mobilization, however, is a major challenge for interest group research. Drawing on existing research practices, we discuss a series of different approaches that may be used to establish a sample of policy issues. The focus then is on the policy-centred stratified sampling procedure used in the INTEREURO project. While our approach has important advantages, we extensively discuss several challenges we faced as well as the procedures we developed in order to deal with these.