Ex Post Facto Study

Ex post facto study or after-the-fact research is a category of research design in which the investigation starts after the fact has occurred without interference from the researcher. The majority of social research, in contexts in which it is not possible or acceptable to manipulate the characteristics of human participants, is based on ex post facto research designs. It is also often applied as a substitute for true experimental research to test hypotheses about cause-and-effect relationships or in situations in which it is not practical or ethically acceptable to apply the full protocol of a true experimental design. Despite studying facts that have already occurred, ex post facto research shares with experimental research design some of its basic logic of inquiry.

Ex post facto research design does not include any form of manipulation or measurement before the fact occurs, as is the case in true experimental designs. It starts with the observation and examination of facts that took place naturally, in the sense that the researcher did not interfere, followed afterward by the exploration of the causes behind the evidence selected for analysis. The researcher takes the dependent variable (the fact or effect) and examines it retrospectively in order to identify possible causes and relationships between the dependent variable and one or more independent variables. After the deconstruction of the causal process responsible for the facts observed and selected for analysis, the researcher can eventually adopt a prospective approach, monitoring what happens after that.

Contrary to true experimental research, ex post facto research design looks first to the effects (dependent variable) and tries afterward to determine the causes (independent variable). In other words, unlike experimental research designs, the independent variable has already been applied when the study is carried out, and for that reason, it is not manipulated by the researcher. In ex post facto research, the control of the independent variables is made through statistical analysis, rather than by control and experimental groups, as is the case in experimental designs. This lack of direct control of the independent variable and the nonrandom selection of participants are the most important differences between ex post facto research and the true experimental research design.

Ex post facto research design has strengths that make it the most appropriate research plan in numerous circumstances; for instance, when it is not possible to apply a more robust and rigorous research design because the phenomenon occurred naturally; or it is not practical to [Page 466]manipulate the independent variables; or the control of independent variables is unrealistic; or when such manipulation of human participants is ethically unacceptable (e.g., delinquency, illnesses, road accidents, suicide). Instead of exposing human subjects to certain experiments or treatments, it is more reasonable to explore the possible causes after the fact or event has occurred, as is the case in most issues researched in anthropology, geography, sociology, and in other social sciences. It is also a suitable research design for an exploratory investigation of cause-effect relationships or for the identification of hypotheses that can later be tested through true experimental research designs.

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