Key concepts

Quantitative research is used to measure and predict, leading to a final course of action. 

Quasi-experimental design is a form of experimental research used extensively in the social sciences and psychology. Quasi experiments resemble quantitative and qualitative experiments, but lack random allocation of groups or proper controls, so firm statistical analysis can be very difficult.

A quasi-experiment is an empirical study used to estimate the causal impact of an intervention on its target population.

A quasi-experiment is an empirical study used to estimate the causal impact of an intervention on its target population. 

Quasi-experimental design involves selecting groups, upon which a variable is tested, without any random pre-selection processes.

For example, to perform an educational experiment, a class might be arbitrarily divided by alphabetical selection or by seating arrangement. The division is often convenient and, especially in an educational situation, causes as little disruption as possible.

After this selection, the experiment proceeds in a very similar way to any other experiment, with a variable being compared between different groups, or over a period of time.

Since the researcher cannot assign certain variables, this would mean the researcher is performing a quasi-experimental study. A quasi-experimental study is defined as an experiment in which participants are not randomly assigned. There are different techniques for how we might overcome this, and I encourage you to explore this in other lessons.

A quasi-experimental design is one that looks a bit like an experimental design but lacks the key ingredient -- random assignment.

Quasi-experimental design is a form of experimental research used extensively in the social sciences and psychology. A quasi-experimental design is one that looks a bit like an experimental design but lacks the key ingredient -- random assignment.

In a quasi-experimental design, the research substitutes statistical "controls" for the absence of physical control of the experimental situation.  The most common quasi-experimental design is the Comparison Group Pre-test/Post-test Design.  This design is the same as the classic controlled experimental design except that the subjects cannot be randomly assigned to either the experimental or the control group, or the researchers cannot control which group will get the treatment.  In other words, participants do not all have the same chance of being in the control or the experimental groups, or of receiving or not receiving the treatment.

There are several types of quasi-experimental designs, including: time series design, equivalent time series samples, equivalent samples materials design, non-equivalent control group, counterbalance designs,separate sample pre-test/post-test, separate sample pre-test/post-test control group, multiple time series design, institutional cycle design, regression-discontinuity design.