USING LATENT SEMANTIC ANALYSIS TO ASSESS KNOWLEDGE - SOME TECHNICAL CONSIDERATIONS

In another article (Wolfe et al., 1998/this issue) we showed how Laten t Semantic Analysis (LSA) can be used to assess student knowledge-how essays can be graded by LSA and how LSA can match students with approp riate instructional texts. We did this by comparing an essay written b y a student with one or more target instructional texts in terms of th e cosine between the vector representation of the student's essay and the instructional text in question. This simple method was effective f or the purpose, but questions remain about how LSA achieves its result s and how the results might be improved. Here, we address four such qu estions: (a) What role does the use of technical vocabulary play? (b) how long should the student essays be? (c) is the cosine the optimal m easure of semantic relatedness? and (d) how does one deal with the dir ectionality of knowledge in the high-dimensional space?