It was the major aim of the study to find out why the Swiss ranking in TIMSS 2 was so much better than the German ranking. Therefore a test population of 84 pupils in Switzerland and 107 pupils in Germany of comprehensive secondary schools had to work on twelve assorted TIMSS-2-items. The main differences to the TIMSS test-design were that they had to elaborate their answers instead of just ticking marks, that they were given plenty of time, and that they had to comment their processings explicitely. Further on they had to comment curricular circumstances, even if they just guessed an answer. Reasons for guessing were raised, too. By the process of evaluating the elaborated solutions it was possible to discriminate different kinds of mistakes, and to find out whether special kinds of mistakes were due to special attributes of the questions posed. One of the main results of the study is that students in Switzerland worked accurately and perseveringly even in topics that were not curricularly valid. This can be proved especially in geometry where the Swiss students handled topics that had not yet been subjects of tuition. They usually commented issue-related, while German pupils tended to skip problems, or in their annotations, shifted their blames. Seemingly by the lot of time given geometry achievements became noticeably better. Curricular mismatches dont seem to be an essential reason for the ranking difference considered. Accepting little or additionally severe mistakes does not change the distance in ranking. Instead, it is shifted evenly. Summarizing, the ranking difference between Switzerland and Germany is not merely an instructional effect, but might be due to educational backgrounds, let it be sociocultural effects or else. Another substantial result of the study at hand is that especially in geometry, a lot of errors may be explainable by the type of questions given that led the students to the wrong trail. Might be this was an intention of the TIMSS-designers to test the students stability. But this, naturally, cant explain the ranking differences considered.