Pre-experimental design is a research design which does not fit the standards of an authentic experiment. Pre-experimental design is usually undertaken for exploratory purposes. There is need for researchers to exercise caution in interpreting and generalizing the results from pre-experimental design and pre-experimental studies. Typical of pre-experimental design is the elimination of a control group, thus it is often called a single-group experiment. Pre-experimental design will not allow definitive conclusions about the causes of the effect observed.
Where two groups did not represent real samples and neither random choice nor a randomized testing were intended, this method is called a pre-experimental design. A pre-experimental design has little control over environmental factors that could affect the outcome of a study. Together with quasi-experiment designs and true experiment designs, pre-experimental designs make the three basic categories of designs with an intervention.
The Main difference between Experimental and Pre-experimental designs is pre-experimental designs lack control of internal validity. An important drawback of pre-experimental designs is that they are subject to numerous threats to their validity. It is often difficult or impossible to dismiss rival hypotheses or explanations. Researchers must exercise extreme caution in interpreting and generalizing the results from pre-experimental studies.
Experimental research is the most familiar type of research design for individuals in the physical sciences and a host of other fields. Experimental research is a classical scientific experiment. The experimental research method is widely used in physical and social sciences, psychology, and education. It is based on the comparison between two or more groups with a straightforward logic, which may, however, be difficult to execute. Quasi-experimental designs and pre-experimental designs are often used when experimental designs are impractical.
Pre-experiments are a simple form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent that's presumed to cause change. Quasi-experimental and pre-experimental designs may be easier to carry out, but they lack the rigor of true experiments.
When true experiments and quasi-experiments are not possible, researchers may turn to a pre-experimental design (Campbell & Stanley, 1963). - Campbell, D., & Stanley, J. (1963). Experimental and quasi-experimental designs for research. Chicago, IL: Rand McNally.
Types of Pre-Experimental Design:
One-shot case study design
One-group pretest-posttest design
A reason that it is often difficult to assess the validity of studies that employ a
pre-experimental design is that they very often do not include any control or comparison
group. Even when pre-experimental designs identify a comparison group, it is still
difficult to dismiss rival hypotheses for the observed change.
Advantages of pre-experimental designs
As exploratory approaches, pre-experimental designs afford a cost-effective way to discern whether a potential explanation is worthy of further investigation.
Disadvantages of pre-experimental designs
pre-experimental designs offer few advantages since it is often difficult or impossible to rule out alternative explanations. The nearly insurmountable threats to their validity are clearly the most important disadvantage of pre-experimental research designs.