There are currently no job-related approaches, in which learning from errors is operationalized as a competence. Such clearly defi ned competencies, which can be measured and promoted, would be particularly relevant for trainees. This dissertation aims to close this desideratum exemplarily for vocational education and training of medical assistants (MFA) in Germany. To this end, empirical and theoretical analyses were used to develop a competency structure model with eight relevant factors. Based on this, a computer-based, job-specifi c competency test was developed and piloted with 97 MFA trainees. In a further study, the test was administered and validated with 386 MFA trainees, which could confi rm the goodness of the competence model and the test.