Ex-Post-Facto Research in Psychology

The independent variable or variables have already occurred in this ex-post-facto study, in which the researcher begins with the observation of a dependent variable or variables. In hindsight, he investigates the independent factors for probable relationships to and impacts on the dependent variable or variables. The most significant distinction between experimental and ex-post facto research is control. In the former, the investigator has manipulative control over the independent variable, but in the latter, this control is not conceivable, nor is randomization. Ex-post facto research requires the researcher to accept things and gather and analyze data in that environment.

What is Ex-Post-Facto Research?

An ex-post facto study is a type of research in which the researcher forecasts the likely reasons for a previously seen outcome. For example, if a youngster is delinquent (that is, engages in criminal acts), the researcher would try to discover the many events that have occurred and the numerous possibilities that might have led to the concerned delinquent behavior. Lack of school discipline, family history, peer influence, neighborhood, or socialization is all factors.

The groups might be skewed in many unforeseen ways. People who learned new arithmetic in elementary school are quite different from those who learned old math. They may have been picked because of their mathematical abilities (or lack thereof). It is also likely that only rich and progressive school districts provided innovative math curricula. As a result, disparities in the student populations from whom the treatment groups were chosen are fairly conceivable. Only urban-industrialized areas received new math curricula, but rural and suburban areas did not. The point is that all of this is speculative. We do not know why some pupils received new math while others received old arithmetic.

Because we could not allocate our students to two groups at random, systematic participant bias is a clear possibility. Our two student groups' average arithmetic competency scores might have differed for reasons other than "new" or "old" math. (A genuine experiment would have required us to randomly assign several students from the same school district to new math classes and about an equal number to old math classes while controlling for all other variables.) We would then give a math competency test in college years later.

Characteristics of Ex Post Facto Research

It is also known as 'causal comparative research' since it is based on an ex-post factor study. Ex-post facto research has several characteristics that set it apart from other forms of research. Some of these qualities are discussed in more detail in the following paragraphs.

  • There is a control or comparison group in the study. Because the research is based on the study of the cause that has already resulted in the consequences, the researcher needs to preserve a control group that can be compared with the real experimental group later on to analyze the reason for an already occurring event.

  • The research's behavior, activity, event, treatment, or independent variable cannot be controlled or modified. Because ex-post research is a study that attempts to forecast causes based on previously occurring actions, the researcher cannot modify or change previously occurring acts or behavior.

  • The study focuses on the consequences. Because the researcher attempts to analyze and forecast the causes of an event or phenomenon, their initial attempt is to focus on the event or phenomenon that has already occurred. Only after thoroughly examining the phenomenon or occurrence does the researcher attempt to discover the reasons for such an event or phenomenon.

  • The study examines an occurrence's 'how' and 'what.' Because the researcher is attempting to understand the causal repercussions of a phenomenon, the research focuses on how and why that phenomenon occurred.

  • Investigates potential impacts and causes. The researcher attempts to analyze the cause-and-effect phenomena of an event, action, or behavior through ex-post facto research.


An example of an ex post facto experiment can help you distinguish it from trials in which the independent variable is modified. In this case, we are interested in how anxious and nonanxious individuals react to loud noise. Do not mistake the "treatment" condition for the loud noise. It is neither a treatment nor an independent variable because it is given to both groups. It is only a task to which all participants must react. The task that all participants execute is our dependent variable measure, which is their reaction to the noise. Membership in a group based on whatever traits the researcher is interested in constitutes the therapy. These qualities are anxious and nonanxious individuals in the current scenario.

Strengths and Weaknesses of Ex-Post Facto Research

No study can be flawless in and of itself, and every approach has advantages and disadvantages, and the same is true in the case of the ex-post factor study. The following are the ex-post facto research's strengths:

  • It is regarded as a particularly important strategy in behavioral studies when variables cannot be changed or altered.

  • Many social (e.g., delinquency) and educational factors may be studied in this manner (e.g., achievements).

  • It is more valuable than experimental research since it can be used to analyze a cause based on the effect, which experimental research cannot do.

  • It saves time and money.

  • It allows the researcher to analyze based on his viewpoint and reach the best possible conclusion.

The following are the shortcomings and limits of ex-post facto research −

  • As previously noted, the researcher cannot modify the independent variables in an ex-post facto study.

  • The researcher cannot randomly allocate the subjects to various groups.

  • The researcher may need help explaining the link between the independent and dependent variables under investigation.


The researcher commits the post hoc fallacy when anticipating the causal links between the variables. The idea of post hoc fallacy states that it is a human predisposition to reach conclusions or make predictions when two things are present, one being the cause and the other being the result. Because delinquency and parenting are linked, we may conclude that delinquency is the result and parenthood is the cause, while the child's peer group may be the true cause.

Updated on: 05-Apr-2023

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