Analyzing developmental trajectories: A semiparametric, group-based approach.

Carnegie Mellon UniversityA developmental trajectory describes the course of a behavior over age or time. Agroup-based method for identifying distinctive groups of individual trajectorieswithin the population and for profiling the characteristics of group members isdemonstrated. Such clusters might include groups of increasers. decreasers,and no changers. Suitably defined probability distributions are used to handle 3data types—count, binary, and psychometric scale data. Four capabilities are dem-onstrated: (a) the capability to identify rather than assume distinctive groups oftrajectories, (b) the capability to estimate the proportion of the population followingeach such trajectory group, (c) the capability to relate group membership probabil-ity to individual characteristics and circumstances, and (d) the capability to use thegroup membership probabilities for various other purposes such as creating profilesof group members.