This report shows how lattice theory can be used to develop quantitative measures of selected characteristics of knowledge structure representations and how these measures can be used to assess individual person's knowledge structure representations in a classroom setting. For a given set of concepts, a knowledge structure can be described by the present or absent connections in the set of all possible pairwise connections between concepts. Under this description, the set of all possible knowledge structure representations for a given set of concepts forms the elements of a complemented, distributive lattice ordered by set inclusion. Measures are developed to assess the dissimilarity between two knowledge structure representations, the local complexity of a concept in a knowledge structure, and the global complexity of a knowledge structure. The effectiveness of these measures in assessing the changes in students' knowledge structure representations in an introductory statistics course is examined using data from T. Ju (1989). (Contains 6 tables, 9 figures, and 39 references.) (Author/SLD)