Key concepts

A pre-experimental design is defined by the absence of a control group and by the absence of random assignment. Only the program participants are tracked in these types of studies.

There are several variations within the category of pre-experimental design, differing only in the number and the timing of outcome measurement points. These variations include:

• Posttest only,
• Pre- and posttest, and
• Pre- and posttest with follow-up.

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

Pre-experimental designs include:

-case study design

-one group pre-test/post-test design

-static group comparison design (cross-sectional study)

Pre-experimental designs are so named because they follow basic experimental steps but fail to include a control group.  In other words, a single group is often studied but no comparison between an equivalent non-treatment group is made.

Types of Pre-Experimental Design

• One-shot case study design
• One-group pretest-posttest design
• Static-group comparison

One-shot case study design

A single group is studied at a single point in time after some treatment that is presumed to have caused change. The carefully studied single instance is compared to general expectations of what the case would have looked like had the treatment not occurred and to other events casually observed. No control or comparison group is employed.

One-group pretest-posttest design

A single case is observed at two time points, one before the treatment and one after the treatment. Changes in the outcome of interest are presumed to be the result of the intervention or treatment. No control or comparison group is employed.

Static-group comparison

A group that has experienced some treatment is compared with one that has not. Observed differences between the two groups are assumed to be a result of the treatment.

Pre-experimental designs are not really considered model experiments because they do not account for extraneous variables which may have influenced the results. 

The three most commonly used pre-experimental designs are the one-shot case study, the one-group pretest posttest and the intact group comparison design.

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

Pre-experimental designs are so named because they follow basic experimental steps but fail to include a control group.  In other words, a single group is often studied but no comparison between an equivalent non-treatment group is made. 

Pre-experiments are the simplest form of research design. In a pre-experiment either a single group or multiple groups are observed subsequent to some agent or treatment presumed to cause change.

A probability sampling method is any method of sampling that utilizes some form of random selection.

In order to have a random selection method, you must set up some process or procedure that assures that the different units in your population have equal probabilities of being chosen.