Three psychometric methods for validating learning hierarchies are applied to one data set derived from responses of grade 10 chemistry students to items representing the skills in a hypothesized hierarchy for the mole concept. Two methods which considered skills in pairs, namely the “test of inclusion” by White and Clark and the “ordering-theoretic method” by Airaisian and Bart produced generally similar results. The third method, by Dayton and Mac-ready, considered the hierarchy as a whole and produced clearer distinctions between alternative hierarchies than the first two methods. The hierarchy derived from this analysis was supported by a test for transfer of learning from subordinate to superordinate skills.