The first part of the paper describes the science framework of the National Educational Panel Study (NEPS) that forms the basis for assessing scientific literacy over a person’s lifespan. The framework and its definition of scientific literacy are influenced by the Programme for International Student Assessment (PISA), by the American Association for the Advancement of Science (AAAS) and by the German educational standards for the end of Grade 10. All of these sources claim that scientific literacy is important for everyone: It forms a basis for general education, has to be applicable to everyday situations and is a source for lifelong learning. Thus, the contexts and components providing the foundation for item development and for measuring scientific literacy had to be chosen accordingly. This paper presents a selection of contexts and content areas that meet this demand and that, at the same time, allow NEPS to be theoretically and methodologically linked to other national and international large scale assessments.The second part of the paper is concerned with the process of item selection. Since NEPS aims to measure scientific literacy over the lifespan, tests for a variety of different age groups have to be developed. Psychometric properties of pilot study tests for children in kindergarten, Grade 6 and Grade 9 are presented. The paper concludes with an outlook of further ways to validate the preliminary findings and of linking tests for different age groups.

Keywords
Scientific literacy; Test development; Panel study; Lifespa