1. Ex-post facto
research
Made by
Psychologist
Stella

2. Ex post Facto research
 Sometimes it is unethical or impossible to manipulate certain
variables to investigate their potential influence on the
dependent variable.
 – Example: How people react after terrorist attack.
 Experimentation is not feasible!
 Solution?
 Ex Post Facto Design, “Ex post Facto” means after the fact.
This method identifies the previous events and present
conditions, then collects data to investigate a possible
relationship between these factors and subsequent behaviors.
 Correlational designs
 Similar: Involves looking at existing circumstances

3. Ex post Facto research
 Experimental designs
 – Similar : It has identifiable dependent and independent variables
 – Difference: No direct manipulation of independent variables
 Problem
 – No way of controlling confounding variables and alternative
explanations, thus, no firm conclusions, but uses data analysis to
pursue truth.
 – Medicine uses this method widely.

4. Simple Ex Post Facto Design
 Similar to experimental design, The only difference is
one of timing.
 – The treatment occurred a long time ago before the study
, so we call it experiment.
 – Researcher hasn’t been responsible for imposing it.

5. Simple Ex Post Facto Design
 This type of design is common for studying
 – The environmental effects such as child abuse,
malnutrition, television viewing habit, etc.
 – Potential influences of pre-existing (hereditary )
characteristics e.g. mental illness, gender etc.
 Can we draw firm conclusions?
 – The most we can conclude is that certain behaviors are
associated with the conditions.
 – Medicine uses this method widely.
 – Other confounding variables might be involved, then no
firm conclusion.

6. Definition
 The danger of the post hoc assumption is that it can, and often
does, leads to erroneous and misleading interpretations of
research data, the effect being particularly serious when the
scientist has little or no control over time and independent
variables.
 Kerlinger (1964) defined ex-post facto research as: that
research 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. He
then studies the independent variables in retrospect for
their possible relations to, and effects on, the dependent
variable or variables (p. 360).

7. Strategies
 There is however some strategies that have been
proposed to ensure that the ex post facto research is
more credible:
1. Matching is done on a subject to subject basis so as to create
matched pairs. The matching criteria will be based on criteria
that enables the researcher to class similar subjects
together. The problem with matching strategies is that the
researcher works with the assumption that the factors he
has selected are the most appropriate and will work with the
dependent variable.
2. Use of homogeneous groups: selecting subject that are
homogenous gives the researcher some degree of control over
the variable and the ability to get the desired results. If a
researcher needs to determine the cause of depression in
specific community, then he can specifically look for similar
community in that area.

8. Strategies
3. Building extra venous variables: This involves selecting
subject who specifically fit the type of data that the
researcher needs. If for instance the researcher identifies
social economic status as a potential variable he will
select to work with a sample that involve student from
low socio economic status. Analysis of covariance is
another strategy that can be used (Ary, & Sorensen,
2009). It is technique that is used to equate groups
depending on specified variable.
4. Partial correlations if the fourth strategy that can be used
to acquire some degree of control over the variable in an
ex post facto research. It involves forming some form of
relations and similarity between two variables used for
the study.

9. Types of ex post Facto research design
 There are two main types of ex post facto research
design.
1. The first is the proactive design. The subjects of this
designed are grouped depending on an already pre
existing independent variable for example subject
studies on scholarship and subjects privately pays for his or
her studies. Once the pre existing groups are
determined measurements are made based on
dependent variable such as level of confidence, class
performance etc.
2. The second category is the retroactive ex post fact where
the researcher seeks that causes of a pre existing
situation the cause in this case will be the
independent variable whereas the pre-existing
situation is the dependent variable.

10. Importance of Ex post facto research
 If properly implemented ex post facto research
can help researchers to clear the air on some
research studies whose findings are
inconclusive. This is especially so for results
gathered through experimental studies. By using
the suggested partial control strategies and
determining alternative hypothesis a
researcher who had first used the
experimental research may find more
conclusive findings if he uses ex post facto
research (Ary, & Sorensen, 2009).

11. Importance of Ex post facto research
 Ex post facto research is also important when
conducting research studies that involve
human beings as the subjects. Many researches
involving human subjects are prone to ethical
issues. This is especially so if the research
involves some form of manipulation that will
negatively affect the participants. In such a
situation the use of ex post facto research will
focus on cause and effect relations rather
than intrusive manipulations that may cross
the ethical boundaries of using human
participants as subjects (Ary, & Sorensen,
2009).

12. Importance of Ex post facto research
 Ex post facto research is important in verifying
already made conclusions on various researches.
This form of research design can therefore be used to
authenticate the conclusions sand findings
made in an in other experimental studies. If the
findings coincide then the findings are deemed to be
true. However, if the findings contradict, then it
create room for more research studies so as to
finding the ultimate truths.

13. Reference
 Ary, D. & Sorensen, C. (2009). Introduction to research
in education. Cengage learning.
 Kerlinger, F. (2010). Foundations of Behavioral
Research. New Delhi: Prism International.

14. Thank You
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