The quality assurance and development of the dual vocational education system necessitates the implementation of evidence-based monitoring of vocational education outcomes. This approach is founded upon the utilization of reliable empirical modelling and the measurement of vocational competence. In the theoretical and empirical foundation, the construct of "vocational competence" has been translated into a measurable form (modelling) and vocational work and business processes have been implemented into test situations (assessment design). The DFG research project, entitled "Competence Development in Vocational Enculturation Processes" (INTERCONNECT, grant number: WI 3597 / KL 3076), builds upon this work and analyses the individual trajectories of competence acquisition and the causal relationships of the proposed competence development model, including its influencing variables. In order to achieve this, an assessment instrument is employed, in addition to a tool designed to capture the specifics of the workplace training situation and relevant control variables.

This dissertation focuses on the measurement of competence changes as part of the project. It examines the validity of the two-dimensional model of vocational competence development using a longitudinal study with N = 458 industrial clerks in their initial vocational training. The validation of the model addresses the following questions: (1) Can the two-dimensional construct of vocational competence be empirically confirmed (validity of the structural model in cross-sectional analysis)?        (2) Can the dynamic construct of vocational competence be empirically confirmed (validity of the developmental model in longitudinal analysis)? (3) Can the boundary of the theoretically grounded two-dimensional construct of vocational competence development be supported through empirical investigation?

The initial two questions are addressed through the utilization of analytical techniques derived from Item Response Theory and Classical Test Theory, including structural tests, correlation analyses, and effect size tests. The results demonstrate that the two-dimensional model of domain-linked and domain-specific competence is stable in both cross-sectional and longitudinal analyses, across different test formats and federal states. Conversely, structural alterations to the model are observed during the training period, as predicted by the theoretical framework. In addressing the third question, a systematic reflection is conducted on two key aspects: firstly, the location of the boundary of the theoretically assumed model; and secondly, the extent to which the empirical boundary aligns with the theoretically defined boundary. In this context, the reflective questions analyzed are as follows: firstly, to what extent can the results of the present study be generalized to other situations and populations; and secondly, whether the empirical application has resulted in a narrowing or broadening of the theoretical construct. The findings contribute to the valid assessment and description of vocational competence development and its success factors in commercial vocational training programs.