A testing-based diagnosing system is implemented. The system has a pro
blem library that collects some suitable problems and associated answe
rs. The answers of each problem are related to misconceptions. Problem
selector in the system provides some problems to test student. Based
on the student's answers, the diagnoser in the system will discriminat
e the student's misconceptions. The problem selector and the diagnoser
are implemented with matrix operations. For evaluating the performanc
e of the system, the topic of basic DC electricity is used as the subj
ect domain. There are nine types of misconceptions found in basic elec
tricity. Based on the experimental results, the system has the satisfa
ctory diagnosis. (C) 1998 Elsevier Science Ltd. All rights reserved.