*C. W. Liew, Joel A. Shapiro, and D. E. Smith*

This paper describes our continuing work on enabling a tutor to evaluate algebraic solutions to word problems in physics. Current tutoring systems require students to explicitly define each variable that is used in the algebraic equations. We have developed a constraint propagation based heuristic algorithm that finds the possible dimensions and physics concepts for each variable. In earlier work we developed techniques that worked for a small set of problems and evaluated them on a small number of students. The work described here covers an extension to and evaluation of a much larger class of problems and a larger number of students. The results show that our technique uniquely determines the dimensions of all the variables in 89% of the sets of equations. By asking the student for dimension information about one variable, an additional 3% of the sets can be determined. Thus a physics tutoring system can use this technique to reason about a student’s answers even when the scaffolding and context are removed.

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