Elff, Martin. 2009. “Political Knowledge in Comparative Perspective: The Problem of Cross-National Equivalence of Measurement”.
The Comparative Study of Electoral Systems (CSES) presents a unique resource for comparative research on political attitudes and behavior. From the beginning, country components of the CSES have contained each at least three items concerned with political information and knowledge. These items vary considerably across countries in terms of question format and question content. Using methods of Item Response Theory (IRT), the paper examines how these aspects impinge on the discriminance and difficulty of the items, both important aspects of their validity as indicators of political knowledge. It shows that the question content is especially important for the items difficulty: Notwithstanding the political context, items that ask for numbers (e.g. of federal states or EU member countries) are much more difficult to answer, given the level of political knowledge. Further, notwithstanding the political context, questions about foreign policy matters have a higher discriminance, that is, can better distinguish between different levels of political knowledge, than other items. The paper concludes with a discussion on how cross-national equivalence of knowledge questions can be enhanced.