4. The method of claim 1 , the assigning further comprising: for each non-valid user response, categorizing said non-valid user response into one of a plurality of categories, wherein the error weight associated with each non-valid user response is based at least in part upon a category of the plurality of categories assigned to the non-valid user response.
4. The method of claim 1 , the assigning further comprising: for each non-valid user response, categorizing said non-valid user response into one of a plurality of categories, wherein the error weight associated with each non-valid user response is based at least in part upon a category of the plurality of categories assigned to the non-valid user response. 6. The method of claim 4 , wherein said plurality of categories comprises at least one category selected from the group consisting of an acoustic error category, a lexical error category, a syntactic error category, and a conceptual error category.