Quasi-Experimental Research

This form of research is approximate to experimental designs, but does not include the random assignment of participants to specific conditions or treatments. They provide an alternative to the study of causal situations where experimentation is impractical, impossible or unethical. They are useful in studying whether or not a certain variable is an ‘indicator’ (rather than a cause) of dependent variables.

There are also many types of Quasi-experimental research designs, including:

Time Series Design

These longitudinal study’s are similar to repeated measures design, and involve the repeated measuring of the dependent variable before, during and after the introduction of the independent variable under study. There are two forms of time-series design, the Interrupted Time-Series Design (which involves the study of one group of the same participants for a period of time), and the Multiple Time-Series Design (which compares two or more groups of the same participants for a period of time).

Regression-Discontinuity Design

(Also known as cross-sectional designs)

This involves a single measurement of different groups that represent different time periods. The rationale being that the different groups represent different experiences of/with the independent variable.

Non-equivalent Groups Basic Pre-test Design

This is similar to the experimental “Basic Pre-test Design”, the difference being however that participants are NOT randomly assigned to groups. Participants are selected by way of ‘matching’ (which involves measuring the extent to which groups of participants differ on a particular characteristic).

Single Participant Design

As the name suggests this study is designs specifically for research involving only one participant or subject. There are three forms of single participant study’s.

1. Case Study

A case study involves the intensive study of one subject over a period of time. Findings from a case-study should be confined only to the person or subject under study, although making generalisations is certainly possible. Case-study’s are also useful in generating hypothesis for further research.

2. Baseline

A baseline study is similar to a case-study, however ‘measurements’ are taken on the subject over a period of time before, during and after ‘treatment’. This is similar to a time-series design.

3. Withdrawal

This design involves the repeated introduction and removal or ‘treatment’ over a period of time. It involves measuring of data at intervals related to the removal and introduction of treatment in order to measure participant response to the ‘treatment’ or variable.