QUASI-EXPERIMENTAL RESEARCH DESIGN

The third category of quantitative research design is quasi-experimental studies. These are similar to experimental studies in that they aim to test the effectiveness of interventions and, therefore, involve manipulating an independent variable.

However, unlike a proper experimental study (e.g., a randomised controlled trial), it lacks the random allocation of participants to certain conditions, such as an intervention/experimental or control group. This may have considerable implications because factors other than those being investigated may affect the findings. These are known as confounding or extraneous variables.

When conducting a randomised controlled trial is not feasible or ethical, quasi-experiments are usually performed. Different types of quasi-experimental studies include, among others (Tab. 7.):

• non-equivalent control pre-test post-test design
• non-equivalent control post-test-only design
• one group pre-test–post-test design and
• time-interrupted series.

Table 7. Features of Quasi-Experimental Research Design

Source: Bloomfield and Fisher (2019).