The research subjects are the freshmen who entered institutes of science and technology in three universities A, B and C in 2015. It studies on percentages of the number of enrolled students who entered universities by various methods. Meanwhile, according to the data, it studies on their answer performances and answer types of questionnaires about buoyancy. Besides, the research compares answer performances and answer types of eighth grade students and ninth grade students so that it discusses “the difference before and after students learn the concepts” and “if their comprehension on concepts will increase with age”. The research results are shown as following: I. The part aiming at education classes (1) The differences before and after students learn concepts are if they can use the buoyancy formula