Missing data for a given cohort of students in a longitudinal study occurs for at least two reasons: either the student has moved or otherwise become unavailable for testing, or the cohort was not in the testing range at a given testing time. A developmental sampling for time of testing x cohort x grade research plan of testing is used to…

A framework for understanding methodological practices from the perspectives of internal validity, external validity, statistical control validity, and construct validity is presented. One hundred doctoral dissertations completed between 1980 and 1988 at a single urban public university were analyzed for various methodological practices and types…