The reasoning ability is very influential on learning outcomes which are generally non-tangible that need formal reasoning to understand them. A student who is able to think in concepts and concepts, students who are able to develop knowledge themselves, then these students will not return to their studies. Thus, it means that formal reasoning abilities possessed by students play an important role in mastering optimal concepts.

From the description above, a research problem can be formulated, namely "how to increase the level of formal reasoning ability to students' knowledge competencies in basic electrical and electronic subjects at Raden Rahmat Mojosari Vocational School?". This study aims to analyze the influence formal reasoning ability in students' knowledge competencies in basic electrical and electronic lessons at Raden Rahmat Mojosari Vocational School. The type of research used is experimental research with factorial design (factorial design).

The results of research on knowledge competencies for students who have a higher formal formal ability level are significantly higher than the competencies of students who have a low formal ability level in basic electrical and electrical learning at Raden Rahmat Mojosari Vocational School.