RESEARCH METHOD COHEN ok

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Ex post facto research
Introduction
When translated literally, ex post facto means ‘from
what is done afterwards’. In the context of social
and educational research the phrase means ‘after
the fact’ or ‘retrospectively’ and refers to those
studies which investigate possible cause-and-effect
relationships by observing an existing condition
or state of affairs and searching back in time for
plausible causal factors. In effect, researchers ask
themselves what factors seem to be associated
with certain occurrences, or conditions, or aspects
of behaviour. Ex post facto research, then, is a
method of teasing out possible antecedents of
events that have happened and cannot, therefore,
be controlled, engineered or manipulated by the
investigator (Cooper and Schindler 2001: 136).
Researchers can report only what has happened
or what is happening, by trying to hold factors
constant by careful attention to the sampling.
The following example will illustrate the basic
idea. Imagine a situation in which there has been a
dramatic increase in the number of fatal road accidents
in a particular locality. An expert is called in
to investigate. Naturally, there is no way in which
she can study the actual accidents because they
have happened; nor can she turn to technology
for a video replay of the incidents. What she can
do, however, is attempt a reconstruction by studying
the statistics, examining the accident spots,
and taking note of the statements given by victims
and witnesses. In this way the expert will be
in a position to identify possible determinants of
the accidents. These may include excessive speed,
poor road conditions, careless driving, frustration,
inefficient vehicles, the effects of drugs or alcohol
and so on. On the basis of her examination, the
expert can formulate hypotheses as to the likely
causes and submit them to the appropriate authority
in the form of recommendations. These may
include improving road conditions, or lowering
the speed limit, or increasing police surveillance,
for instance. The point of interest to us is that in
identifying the causes retrospectively, the expert
adopts an ex post facto perspective.
Ex post facto research is a method that can
also be used instead of an experiment, to test
hypotheses about cause and effect in situations
where it is unethical to control or manipulate the
dependent variable. For example, let us say that we
wished to test the hypothesis that family violence
caused poor school performance. Here, ethically
speaking, we should not expose a student to family
violence. However, one could put students into
two groups, matched carefully on a range of
factors, with one group comprising those who have
experienced family violence and the other whose
domestic circumstances are more acceptable. If
the hypothesis is supportable then the researcher
should be able to discover a difference in school
performance between the two groups when the
other variables are matched or held as constant as
possible.
Kerlinger (1970) has defined ex post facto
research as that in which the independent variable
or variables have already occurred and in which
the researcher starts with the observation of a
dependent variable or variables. The researcher
then studies the independent variable or variables
in retrospect for their possible relationship to, and
effects on, the dependent variable or variables.
The researcher is thus examining retrospectively
the effects of a naturally occurring event on a
subsequent outcome with a view to establishing
acausallinkbetweenthem.Someinstancesof
ex post facto designs correspond to experimental