One key characteristic of a quasi-experiment is that one or more conditions of a true experiment cannot be met. This often includes the fact that there is no random allocation to the treatment or control conditions in the experiment. So if there is no random allocation, but there is still an IV hypothesized to have an effect on a DV, the study can be classified as being quasi-experimental.
If something is quasi it means that it’s apparently something, or seems to be something, but it’s not quite. So a quasi-experiment appears to be an experiment, but it’s “not quite.”
This means that sometimes to determine if a study is quasi-experiment or a true experiment, you have to dig deep into the methodology.
A good example to compare a true experiment and a quasi-experiment is by looking at two very similar experiments (summaries available here):
Lazar et al. (2005) on the effects of meditation on the brain
Desbordes et al. (2005)on the effects of mindfulness on brain activity
In Lazar’s experiment they compared the brains of meditation experts with a control group of participants that had no meditation experience. In this case, the researches could not randomly assign participants to be an expert or a control.
Since there is still an IV (meditation experience) that is hypothesized to have an effect on a DV (grey matter in the brain), this is an experiment. But because not all conditions of a true experiment can be met (in this case, there can be no random allocation), we can classify this as a quasi–experiment.
Desbordes et al. studied mindfulness (a type of meditation) on the activity in the brain but this is a true experiment because they controlled for extraneous variables and randomly assigning participants to the treatment and control groups (You can read more about this study here).
These two studies work well together and can be partnered up to discuss a range of topics, including:
- The use of technological techniques
- Experimental methods (quasi and true experiments) to study:
- The brain
- cognitive processes
Traditionally “the experimental method” (which includes true, quasi, natural and field experiments) has been classified as one research method by the IB. This means that if you are asked an essay question to discuss or evaluate the use of one research method, you could identify the experimental method as your method, and include these two studies in your answer. The contrast between quasi and true experimental design could work well for the discussion or evaluation part of the answer.