P = The general population
U = An unrandomized group
X = The intervention (the independent variable)
O = The post-intervention observation (the dependent variable)

Type:

Pre-experimental Research Design

What it is:

The single shot case study is the simplest research design. In this design, some treatment is administered to an unrandomized group arbitrarily selected from the general population. Then the results are observed and recorded.

Method:

Step One

Choose an arbitrary group from the general population "P" and designate this group as the experimental group "U".

Step Two

Administer the intervention "X" to the experimental group "U".

Step Three

Observe group "U" and record the outcome of the interaction on the experimental group "O"

Step Four

Summarize, analyze, and report the results.

Threats to Validity

History

Lack of control introduces potential history risk.

Maturation

Lack of control introduces potential maturation risk.

Testing Effects

Not a factor in single test designs.

Instrumentation

Probably insignificant. Depends on the method chosen.

Statistical Regression

Not a factor in a single test design.

Selection

Makeup of the unrandomized group likely to affect results.

Attrition

Lack of control introduces potential attrition risk.

Interaction

Must always be considered.

Remarks:

The critical flaw is the absence of anything to compare the observations with. For example, suppose one were to change his or her daily diet and began to lose weight. From that, it is concluded that the diet change was effective ignoring the effect of other factors such as increased exercise. Although often found in many contexts, this design rarely produces meaningful results and the resulting data should be carefully considered.

—By Douglas E. Greathouse, MA.(2007)