Quantitative Research Designs: Descriptive non-experimental, Quasi-experimental or Experimental?
Students often have difficulty classifying
quantitative research designs. In quantitative research, designs can be classified into one
of three categories: descriptive non-experimental, quasi-experimental or experimental. To identify
which of these designs your study is using follow the steps in this video.
First, ask yourself if the researchers did anything to the participants. More specifically,
was there an intervention? Interventions include things like support
groups, educational sessions, treatments for a condition or some other variable that is
being tested. If people would not normally have something without being in the study
but the researcher gives it to them to see what it will do than that is an intervention.
You may also see research texts call this a manipulation. Essentially, the researcher
did something to people to provoke some kind of measurable result.
If the answer is yes, there was an intervention, then the study is either a quasi-experimental
or experimental. I will tell you how to decide in a moment.
If the answer is no, the study is descriptive non-experimental. Sure, you could be more
specific in the description of the design, but for the purposes of grouping your research
in a literature review this label is often sufficient at an undergraduate level.
Descriptive non-experimental studies may also be called observational. Some examples of
more specific labels include case control, cohort and correlational studies. For more
information about these non-experimental designs please visit the research playlist below this
video and watch the video about research paradigms and methodology.
To find out if the design is experimental ask yourself if it is a randomized controlled
trial. Randomized controlled trials are considered the gold standard or “best” possible design
(in quantitative research). You may also hear randomized controlled trails referred to as
true experiments. However, in the real world it is difficult to conduct a true randomized
controlled trial in many situations, which means that a lot of studies are done that
are not classified as randomized controlled trials.
Randomized control trials have three key components: a random sample, a control group and an intervention.
If your study is truly a randomized control trial it should say in the abstract and/or
the methods section of the article. If it doesn’t say then it is likely that the study
is either descriptive non-experimental or quasi-experimental. You can tell the difference
by looking into the methods section further. Recall that if the intervention is missing
the study is not an experiment. As we just discussed, this type of research is observational
in nature and therefore is classified as a descriptive non-experimental study.
If there is no control group than the study is quasi-experimental. A control group is
a group of people that enter the study but do not receive the intervention under study.
Instead, they are used for the purpose of comparison.
If the sample was not randomized properly or adequately or even at all then the study
is also quasi-experimental. You may also see this type of study being called a non-randomized
trial. Many randomization strategies exist, but basically if a study is randomized it
means that everyone who entered the study had an equal chance of receiving the intervention
under study. You may see some studies indicate that they were partially randomized. These
studies still do not count as true experiments. If your study has a random sample, control
group and intervention than it is a randomized control trial.
Sometimes I see students that are confused about the study design because of terms that
relate to the length of time the study was conducted or the sampling process. While you
are right that these terms relate to study designs they are not broad enough to represent
the methodology of the study and therefore do not give enough information to the reader
about the study design. Terms like cross-sectional and longitudinal
tell you how much time the study was conducted over. Cross sectional means that data were
collected at one point in time. Longitudinal means that data were collected over a long
period of time. These terms alone will not tell you if the study is descriptive non-experimental,
quasi-experimental or experimental. If you use these words to describe your study design
in the absence of one of the labels we discussed in this video you will not have given your
teacher enough information about the study design to properly classify it.
Other confusing terms often relate to the way samples were collected, like convenience
sampling. Convenience sampling means that the sample was readily available or accessible
to the researchers. This term will give you the hint that the study does not have a random
sample and is therefore not a randomized controlled trial, but you still need to classify it further
as descriptive non-experimental or quasi-experimental. To decide how to classify the design of a
study you are looking at, follow the steps outlined in this video. Ask yourself the following
three questions: Was there an intervention?
Is there a control group? Was the sample random?
The answer to these questions will tell you how to classify the design of any quantitative
study into one of these three categories: descriptive non-experimental, quasi-experimental
or experimental. Check with your teacher to see what other labels they may be expecting
in the description of your research design just in case they want more detail.
If you are looking for more detailed information you are welcome to check out my eBook or related
videos. The eBook is best in PDF format, but is also available in other formats at the
links below this video. If there is anything else you need please comment to let me know
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