1. Handling of student mistakes in the Logic Tutor The principle of “cascading” mistakes PowerPoint show prepared for our article in IMEJ D. Abraham, E. Crawford, L. Lesta, A. Merceron and K. Yacef University of Sydney

2. Level 0: Syntactical mistakes Syntactical error is detected by the Parser

3. Level 1: General basic mistakes “Incorrect line number” Here the Expert Module detects that the result could be achieved by applying the rule with lines other than those specified by the student Mismatch between the lines referred to, the rule used and the formula given

4. Level 1: General basic mistakes Invalid application of rule Here the Expert Module detects that the result could be achieved by applying another rule than the one specified by the student Mismatch between the lines referred to, the rule used and the formula given

5. Level 2: More specific mistakes Use of Simplification without Commutation Mismatch between the lines referred to, the rule used and the formula given Here the Expert Module detects that the result could be achieved by applying Commutation before Simplification