Longitudinal-Experimental Studies

Abstract

Longitudinal-experimental studies are follow-up surveys that include an experimental intervention. The main advantage of these surveys is that it is possible to study both the natural history of development and the impact of interventions in one research project. This chapter focusses on large-scale community surveys with repeated personal interviews with participants spanning at least 5 years. It reviews the advantages and problems of longitudinal surveys, randomized experiments, and longitudinal-experimental designs. To some extent, the advantages of one method compensate for the problems of the other. This chapter also reviews the advantages and problems of quasi-experimental analyses in longitudinal surveys. There have been many longitudinal-experimental studies in criminology in which persons who did or did not receive an intervention were followed up for several years; the most important of these are reviewed here. However, no criminological study has yet been completed that includes at least 3 years of personal contact with participants before and after an intervention. Such a study should be mounted.