We present and analyze the employment of the Diproche system, a natural language proof checker, within a one-semester mathematics beginners lecture with 228 participants. The system is used to check the students' solution attempts to proving exercises in Boolean set theory and elementary number theory and to give them immediate feedback. The benefits of the employment of the system are assessed via a questionnaire at the end of the semester and via analyzing the solution attempts of a subgroup of the students. Based on our results we develop approaches for future improvements.

The Diproche system, an automated proof checker for natural language proofs specifically adapted to the context of exercises for beginner's students similar to the Naproche system by Koepke, Schröder, Cramer and others, uses a modification of an automated theorem prover which uses common formal fallacies intead of sound deduction rules for mistake diagnosis. We briefly describe the concept of such an'Anti-ATP' and explain the basic techniques used in its implementation. Learning how to prove is one major obstacle of the introductory phase of university education in mathematics. It requires practice, i.e. exercises, which need to be corrected, which is both an expensive and time-consuming task. This limits the way in which corrections can usually enter into the process of solving proof exercises as feedback.