Presentation on Ex-Post Facto Research

1. MED-2016-18
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 engineered or manipulated by the investigator. 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, she 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.
Kerlinger (1970) has defined ex post facto research more formally 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. She 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 a causal link between them. Interestingly, some instances of ex post facto designs correspond to
experimental research in reverse, for instead of taking groups that are equivalent and subjecting them to different treatments so
as to bring about differences in the dependent variables to be measured, an ex post facto experiment begins with groups that are
already different in some respect and searches in retrospect for the factor that brought about the difference. Indeed Spector
(1993:42) suggests that ex post facto research is a procedure that is intended to transform a non-experimental research design
into a pseudo-experimental form.
Two kinds of design may be identified in ex post facto research—the co-relational study and the criterion group study. The
former is sometimes termed ‘causal research’ and the latter, ‘causal-comparative research’. A co-relational whilst
Ex post facto-research
Experimental research, where the researcher manipulates the independent variable, whilst the dependable variable are controlled
with the aim of establishing the effect of the independent variable on the dependable variable, is also applicable.
The term ex post facto according to Landman (1988: 62) is used to refer to an experiment in which the researcher, rather than
creating the treatment, examines the effect of a naturally occurring treatment after it has occurred. In other words it is a study
that attempts to discover the pre-existing causal conditions between groups.
It should, however, be pointed out that the most serious danger of ex post facto-research is the conclusion that because two
factors go together, one is the cause and the other is the effect.
Jacobs et al. (1992: 81) refers to the following procedures when conducting ex post facto-research:
- The. first step should be to state the problem.
- Following this is the determination of the group to be investigated. Two groups of the population that differ with regard to the
variable, should be selected in a proportional manner for the test sample.
- Groups, according to variables, are set equal by means of paring off and statistical techniques of identified independent and
dependent variables.
- Data is collected. Techniques like questionnaires, interviews, literature search etc:. are used to determine the differences.
- Next follows the interpretation of the research results. The hypothesis is either confirmed or rejected.
Lastly it should be mentioned that this type of research has shortcomings, and that only partial control is possible.
after the fact answers about what happened to the measured variable
Characteristics of Ex Post Facto Research
page 1 / 3

2. MED-2016-18
Description:
space
Description:
space
Description:
space
Description:
space
Description: space
• There is a control or comparison group
• Intact groups are used
• The treatment is not manipulated, it has already occurred.
Ex Post Facto (Causal- Comparative) Research
Description:
space
Description:
space
Description:
space
Description:
space
Description:
space
Description:
space
• Explores possible causes and effects
• The independent variable is not manipulated,
it has already been applied
• Focuses first on the effect, then attempts to
determine what caused the observed effect.
Ex Post facto Research - A lot of research investigates events that have already occurred and implies cause - and
effect relationships from the results (Latin for after the fact). Ex Post facto research is used to study groups that are
similar and have had the same experience except for one condition. The effect of the differing condition on some
other variable can then be assessed. Thus, there are treatment and control groups, but the effect has already
occurred as the researcher begins the study. Because there is no active manipulation of conditions nor is there
random assignment of subjects to groups, causative conclusions that can be drawn from this type of research are
tentative at best.
Ex post facto research
page 2 / 3

3. MED-2016-18
a type of research that begins with data already collected, or research technologies applied to events not originally intended for
reseach purposes.
Causal-comparative research or ex post facto research is used to determine the cause or reason for existing differences in the
behavior in a group. The basic design involves selecting two groups differing on some independent variable and comparing them
on some dependent variable.
Causal Comparative or Ex Post Facto Research Design - Maternity Satisfaction with their Hospital Stay
Ex-post Facto
Research question: Does learning English in elementary school affect the university students’ speaking ability?
Design:
There is no randomization here.
You select the subjects on the basis of a certain existing condition.
You do not give treatment to any group because:
1. the “treatment” already happened in the past and you can no longer do anything about it, or
2. it is unethical to give a treatment to the ex-post facto group.
The ex post facto is similar to an experiment, except the researcher does not manipulate the independent variable, which has
already occurred in the natural course of events. The researcher simply compares groups differing on the preexisting
independent variable to determine any relationship to the dependent variable. Because there is no manipulation or control of the
independent variable, one must be very careful regarding the conclusions that are drawn about any observed relationship. The
variables in this type of research differ in kind rather than in amount. Later, we refer to these as categorical variables. For
example, to answer the question, “what is the effect of part-time work on school achievement of high school students?” one
would use the ex post facto method. The researcher would not manipulate the lives of high school students by having some take
part-time jobs and others not; instead the researcher would identify students who already work part-time compare their
achievement with that of students who do not work. Because researchers lack control over many factors, they must be especially
careful in interpreting the results of ex post facto investigations. They do not establish a simple causal relationship among the
variables of a study.
Powered by TCPDF (www.tcpdf.org)
page 3 / 3