Pre-Post Test Design

Suppose a teacher wants to measure the impact of their teaching techniques on students’ learning outcomes. A simple way of measuring the impact would be as follows:

The teacher will conduct a test for students before teaching the class. After which, they will teach the class using a particular technique, and take another test for the same class with a similar level of difficulty. Finally, the teacher analyses the difference in score of these two tests to measure the impact of their teaching.

The evaluation design used here is referred to as Pre-Post Test Design, and it is an experiment in which outcome or impact indicator measurements are taken before and after the treatment is administered (Zach, 2020) using a standard survey pre and post the intervention. (EMpower, n.d.).

Pre-Post Test Designs are flexible; and can be used across non-experimental, experimental and quasi-experimental research settings. While it has a treatment group, it may or may not include a control group (Zach, 2020). Although, it is especially used in non-experimental settings within the same treatment group when either the interventions are universally applicable, or too complex to generate a matched comparison group (Kultar et al., 2017).

In the presence of a control group, Pre-Post test designs have a strong internal validity but face challenges in achieving external validity (Shuttleworth, 2009). However, when done in a non-experimental setting, since there is no baseline measurement against groups that remained completely untreated, it becomes challenging to find whether the pre-testing process influenced the results (Shuttleworth, 2009), thus weakening internal validity. For example, children giving a pre-test may try a harder in their lectures and try to outperform children who were not given a pre-test; thus making the test results an outcome of the experimental process, rather than administering the treatment alone (Shuttleworth, 2009).

Advantages of Pre-Post Test Design (meera, n.d.):

• Pre-post-test design are relatively simple to implement
• It controls for variables that may influence outcomes prior to administering the intervention
• Compared to retrospective pre and post-tests, or post-tests, they deliver better evidence for effectiveness of the intervention

Disadvantages of Pre-Post Test Design (meera, n.d.):

• In the absence of a control group, it cannot account for confounding variables or non-programmatic influences on outcome indicators.
• When self-reporting measures are used, in the absence of a control group, it may lead to over-estimation of a particular indicator at baseline (due to lack of knowledge) and accurate estimation at endline (after undergoing treatment); thus, creating erroneous conclusions.

For a broad overview #