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PRE-EXPERIMENTAL DESIGN

Sociology Index, Sociology Books 2011

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.

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 randomisation were intended, this method is called a pre-experimental design according to the system conceived by CAMPBELL and STANLEY (SCHWARZ 1970). 

A pre-experimental design has little control over environmental factors that could affect the outcome of a study.

For example, a one-group, pretest/posttest design doesn't even use another group for comparison. But such a design does provide some evidence of program impact (with major limitations in the conclusions that can be drawn) and is commonly used when more elaborate designs are not possible.

One-group designs can be strengthened as an evaluation method by simply adding a comparison group.

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.

Types of Pre-Experimental Design
One-shot case study design
One-group pretest-posttest design
Static-group comparison

Validity of Results
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.

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
As exploratory approaches, pre-experiments can be a cost-effective way to discern whether a potential explanation is worthy of further investigation.

Disadvantages
Pre-experiments 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.

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