A probabilistic hypothesis testing procedure to assess the fit of hypothesized hierarchical structures for test item data is discussed. Statistical procedures are presented which are useful for evaluating the fit of data of a certain class of probabilistic models. These models apply to sets of dichotomous (O,1) responses for which there are posited to exist a priori dependence structures. Examples of relevant types of data are success/failure patterns from Piagetian tasks, learning hierarchies, and domain referenced tests, as well as agree/disagree responses from attitude tests. (Author/RC)