A quasi-experimental design can be an excellent alternative when ethical or practical considerations preclude conducting actual experiments, although the research approach has some shortcomings.1
Index
- 1 Quasi-experimental design: straight to the point
- 2 Definition: Quasi-experimental design
- 3 Quasi-experience versus true experience
- 4 3 types of quasi-experimental design
- 5 When is a quasi-experimental design relevant?
- 6 advantages and disadvantages of a quasi-experimental design
- 7 frequently asked questions
- 8 fuentes
Quasi-experimental design – in summary
- Due to the manipulation of independent variables, quasi-experimental researchextinguishThe directivity problem.
- An almost experimental designhandlean independent variable without random assignment of individuals to order terms or conditions.
- A quasi-experimental design is a distinctive research technique because it isdistinguishablefor what you lack
definition: quasi-experimental design
A quasi-experimental project, like a real experiment, attempts to:cause and effectconnection between aregardlessmidependentVariable.
Unlike a real experiment, a quasi-experimental design is not based on random assignment. Non-random criteria are used to assign subjects to groups.2
Quasi-experience versus true experience
There are numerous contrasts between real and quasi-experimental designs.
| true experimental design | Quasi-experimental design | |
| Assignment to treatment | Treatment and control groups will be randomly assigned by an investigator. | Another non-random method is used to assign subjects to groups. |
| control over treatment | Treatment is usually designed by the investigator. | Of course, the investigator has no influence on the treatment; Instead, they examine pre-existing groups that have subsequently received various treatments. |
| use of control groups | Requires the use of treatment and control groups. | The use of control groups is not mandatory. |
Example of a quasi-experimental vs. experimental design. real
Let's say you're curious about how a new psychological treatment is affecting people with depression.
True Experimental Design:
To carry out a real experiment, one mustal azarAssign the new treatment to half the patients in a psychiatric hospital. The other half of the sample, the control group, receives normal treatment for depression.
Patients fill out a symptom sheet every few months to determine if the new treatment is significantly more effective (or less effective) than the traditional treatment.
However, for ethical reasons, psychiatric facility administrators may deny you permission to randomly assign your patients to treatments. No real experiment can be done in this situation.
Instead, you can use a quasi-experimental design.
Quasi-experimental design:
They note that some of the clinic's psychotherapists decided to try the new treatment, while others dealing with comparable patients decided to stick with the standard approach.
You can use these existing groupscomparethe development of symptoms from patients receiving the new therapy to those receiving the usual treatment.
Even if the groups were not randomized, if you correctly account for any biases between them, you can be sure that any differences must be attributed to treatment and not to other confounding variables.
3 types of quasi-experimental design
One can distinguish between the three most common types of quasi-experimental design. Next, we discuss the nonequivalent group design, the regression discontinuity, and natural experimentation.
non-equivalent group design
Group projects that are not equivalent are ahybridexperimental and quasi-experimental methods. This is because it exploits both properties. Similar to a real experiment, non-equivalent group designimplementedpre-existing groups: treatment and control groups are assumed to be comparable. neverthelessLackarandomizationwhich defines a quasi-experimental design.
Researchers ensure that third parties or confounding variables do not influence them throughout the pooling process. Consequently, the groupings are as comparable as possible.2
Example:
- They believe that an after school program can lead to better grades.
- They select two groups of children, one that attends a school that implements the new program and the other that does not.
- You can determine if the program is affecting grades by comparing students who participate in the program with those who do not.
regression discontinuity
The Regression Discontinuity Design, or RDD, is a quasi-experimental method forcalculateaA hita treatment or intervention. This is accomplished through a mechanism known as a "cutoff," which assigns treatment based on suitability.
Therefore, participants above the cutoff will be assigned to a treatment group, participants below the cutoff will not. The distinction between these two departments is negligible.2
Example:
- Some high schools in the United States are reserved for high-achieving students who must achieve a minimum score on an entrance exam to be admitted. Those who pass the evaluation are systematically different from those who do not.
- However, because the exact score is arbitrary, students who are close to scoring barely pass the tests and those who narrowly fail tend to have very similar scores with only minor differences between them, mostly due to chance. Therefore, you can assume that any difference in results is due to the schools the students attended.
- You can look at the long-term outcomes of these two groups of children to determine the impact of attending a selective school.
natural experiments
In laboratory and field experiments, researchers are often tasked with assigning individuals to a specific group. During a natural experiment, subjects are randomly or accidentally assigned to the treatment group by an external event or situation.
Because the experiments are natural.observation,They are not considered real experiments, although some use random assignment.
Researchers can use the independent variable, even if they have no control over it, to study the effect of treatment.
Example:
- One of the most famous natural experiments is the Oregon Health Study. In 2008, Oregon agreed to allow other low-income people to participate in Medicaid, the health insurance program for low-income people in the United States.
- Not having the money to consider everyone who qualified for the program, they used a random lottery to allocate spots in the program.
- The investigators evaluated the effect of the program using recruits as the randomized treatment group and those who were eligible but not lottery winners as the control group.
When is a quasi-experimental design relevant?
Although actual experiments have higher internal validity, you may choose to use a quasi-experimental design for ethical or practical reasons.
ethical reasons
Sometimes it would be unethical to arbitrarily offer or refuse a treatment, making it impossible to conduct a real study. In this situation, a quasi-experimental design can be used to investigate the precise causal relationship without ethical concerns.
A notable example is the Oregon Health Study. It would be unethical to arbitrarily provide health insurance to certain people and exclude others from coverage solely for research purposes.
practical reasons
Despite their greater internal validity, true experiments can beCaro.Furthermore, a sufficient number of participants is required to justify the experiment. In a quasi-experimental design, on the other hand, you can use data that has already been collected.2
Pros and cons of a quasi-experimental design
| advantage | Unlike |
| • Gives researchers control over variables and allows them to manipulate them. | • It has less internal validity than real experiments. |
| •The quasi-experimental method is compatible with various experimental procedures. | •It is prone to human error. |
| •Offers a higher level of portability. | • Allows investigator bias to enter the equation.2 |
frequent questions
What is a quasi-experimental project?
A quasi-experiment is a research project intended to prove a cause-and-effect relationship.
What is a random assignment?
Random assignment is used in experimental surveys to randomly distribute subjects into different groups.
This strategy ensures that each member of the sample is randomly assigned to a control or experimental group.
When should I use a quasi-experimental design?
A quasi-experimental design is most beneficial in cases where conducting an actual experiment would be unethical or impractical.
ointernal validityof a study based on a quasi-experimental design is inferior to actual experiments, but its external validity is often higher because it uses real-world interventions rather than invented laboratory conditions.
Fuentes
¹ Master class. “Quasi-experimental design: types, examples, advantages and disadvantages.” June 16, 2022.https://www.masterclass.com/articles/quasi-experimental#learn-more.
² Vox Co. "A Complete Guide to Quasi-Experimental Design: Explanation, Methods, and Frequently Asked Questions." September 27, 2021,https://www.voxco.com/blog/quasi-experimental-design-explanation-methods-and-faqs.
FAQs
What are the 7 steps of experimental design? ›
- Set objectives.
- Select process variables.
- Select an experimental design.
- Execute the design.
- Check that the data are consistent with the experimental assumptions.
- Analyze and interpret the results.
- Use/present the results (may lead to further runs or DOE's).
Section 2: Experimental Studies
True experiments have four elements: manipulation, control , random assignment, and random selection. The most important of these elements are manipulation and control. Manipulation means that something is purposefully changed by the researcher in the environment.
The components of experimental design are control, independent variable and dependent variable, constant variables, random assignment and manipulation.
What three things are important to do in a proper experimental design? ›In general, designs that are true experiments contain three key features: independent and dependent variables, pretesting and posttesting, and experimental and control groups. In a true experiment, the effect of an intervention is tested by comparing two groups.
What are the 3 types of experiments? ›The three main types of scientific experiments are experimental, quasi-experimental, and observational (non-experimental). Experimental, or randomized control, is the highest level of scientific experimentation.
What are the 3 types of experimental design? ›- Pre-experimental Research Design. ...
- True Experimental Research Design. ...
- Quasi-experimental Research Design.
A factor of an experiment is a controlled independent variable; a variable whose levels are set by the experimenter. A factor is a general type or category of treatments. Different treatments constitute different levels of a factor.
What is basic experimental design? ›Experimental design is the process of carrying out research in an objective and controlled fashion so that precision is maximized and specific conclusions can be drawn regarding a hypothesis statement. Generally, the purpose is to establish the effect that a factor or independent variable has on a dependent variable.
What is needed for a good experimental design? ›To design a controlled experiment, you need: A testable hypothesis. At least one independent variable that can be precisely manipulated. At least one dependent variable that can be precisely measured.
What factors are important in designing a good experiment? ›- The set of explanatory factors.
- The set of response variables.
- The set of treatments.
- The set of experimental units.
- The method of randomization and blocking.
- Sample size and number of replications.
Which is the main purpose of an experimental design? ›
Experimental design is used to establish the effect an independent variable has on a dependent variable. An experimental design helps a researcher to objectively analyze the relationship between variables, thus increasing the accuracy of the result.
What are the 2 types of variables needed for an experiment? ›You can think of independent and dependent variables in terms of cause and effect: an independent variable is the variable you think is the cause, while a dependent variable is the effect. In an experiment, you manipulate the independent variable and measure the outcome in the dependent variable.
What are the 2 main types of experimental research design? ›Experimental research can be grouped into two broad categories: true experimental designs and quasi-experimental designs. Both designs require treatment manipulation, but while true experiments also require random assignment, quasi-experiments do not.
What are the two main variables in an experiment *? ›Independent variables (IV): These are the factors or conditions that you manipulate in an experiment. Your hypothesis is that this variable causes a direct effect on the dependent variable. Dependent variables (DV): These are the factor that you observe or measure.
What is experimental design *? ›Experimental design is a technique that enables scientists and engineers to efficiently assess the effect of multiple inputs, or factors, on measures of performance, or responses.
What are methods of experiments? ›Experimental methods are research designs in which the researcher explicitly and intentionally induces exogenous variation in the intervention assignment to facilitate causal inference. Experimental methods typically include directly randomized variation of programs or interventions.
What is the most common type of experimental design? ›Three of the more widely used experimental designs are the completely randomized design, the randomized block design, and the factorial design. In a completely randomized experimental design, the treatments are randomly assigned to the experimental units.
What is control of experiment? ›When conducting an experiment, a control is an element that remains unchanged or unaffected by other variables. It's used as a benchmark or a point of comparison against which other test results are measured. Controls are typically used in science experiments, business research, cosmetic testing and medication testing.
What affects the validity of experiments? ›The validity of your experiment depends on your experimental design. What are threats to internal validity? There are eight threats to internal validity: history, maturation, instrumentation, testing, selection bias, regression to the mean, social interaction and attrition.
What are the seven 7 Steps of research process? ›- Step 1: Identify and Develop Your Topic. ...
- Step 2: Find Background Information. ...
- Step 3: Use Catalogs to Find Books and Media. ...
- Step 4: Use Databases to Find Journal Articles. ...
- Step 5: Find Internet Resources. ...
- Step 6: Evaluate What You Find. ...
- Step 7: Cite What You Find Using a Standard Format.
What are the steps of experimental design? ›
- Step 1: Define your variables. You should begin with a specific research question. ...
- Step 2: Write your hypothesis. ...
- Step 3: Design your experimental treatments. ...
- Step 4: Assign your subjects to treatment groups. ...
- Step 5: Measure your dependent variable.
- Step 1: establish your question and set variables. ...
- Step 2: build your hypothesis. ...
- Step 3: designing experimental treatments. ...
- Step 4: categorize into treatment groups.