In the CER model, the diagnosis of student learning problems mainly depends on the prerequisite relationships between the concepts to be learned. Consider two concepts to be learned, say Ci and Cj. If Ci is a prerequisite to efficiently performing the more complex and higher level concept Cj, then a concept-effect relationship Ci->Cj is said to exist. For example, to learn the concept “subtraction of positive integer,”one may first need to learn “addition of positive integer”, while learning “division of positive integer” may require first learning “subtraction of positive integer” and “multiplication of positive integer”. Fig. 1 presents an illustrative example of the concept-effect relationships, which are important in diagnosing student learning problems. For example, if a student fails to answer most of the test items concerning “division
of positive integer” due to a lack of understanding of the questions posed or because of carelessness, the problem is likely because the student has not thoroughly learned “division of positive integer” or its prerequisite concepts (such as “subtraction of positive integer” or “multiplication of positive integer”). Therefore, teachers could identify the learning problems of students by tracing the concept-effect relationships (Cheng et al., 2005; Hwang, 2003a; Hwang, Tseng, et al., 2008).
In the CER model, all of the possible learning paths will be taken into consideration to find the poorly-learned paths. In the illustrative example given in Fig. 1, there are two learning paths for the subject unit: