What is experimental design and what are the examples and the categories of experimental design?
Experimental design is a central feature of the scientific method and it involves evaluating an independent variable against a dependent variable.
A common example of experimental design is a clinical trial that involves several research participants organized into control and treatment groups.
Experimental design involves the process of conducting research in an organized and controlled fashion to enable the maximization of precision.
What Is Experimental Design?
Experimental design is a central feature of the scientific method and it involves evaluating an independent variable against a dependent variable.
Generally, the independent and dependent variables have a cause-and-effect relationship. The former is manipulated in an experiment.
The observer caused the independent variable to change and it directly affects the dependent variable. Once the independent variable is changed, the dependent variable will also change as a result.
During experiments, the researcher must define variables, measure the dependent variable, and also assign subjects.
Experimental design is a method to test the hypothesis by using a series of simple steps. Its purpose is to develop controlled conditions during an experiment to reduce exposure to interference from the outside.
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Categories of Experimental Design
The three categories of experimental design include pre-experimental design, quasi-experimental design, and true experimental design.
Pre-Experimental Design
This involves testing the effects of the independent variable on one participant or a small group of participants. An example is a case study.
Quasi-Experimental Design
It involves testing the effect of the independent variable on a group of participants that were not just randomly appointed to treatment and control groups. An example is purposive sampling.
True-Experimental Design
This involves testing the effects of the independent variable on a group of participants that are not just randomly appointed to treatment and control groups. An example is a clinical trial.
Experimental Design Examples
The following are experimental design examples and their types;
Mood State Study
- Type: Pre-Experimental Design
A group of psychologists are eager to study how mood affects behaviours generally.
They came up with an idea and made a four minutes video showing scenes from famous Hollywood films. The psychologist then recruited a few individuals to watch the heart-wrenching video.
They measured the mood states of the participants after the video ended.
The result of the experiment shows that the participants were in a negative mood. However, the psychologists cannot be fully confident in the clip’s effectiveness as there was no control group.
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Math Games and Learning Study
- Type: Quasi-Experimental Design
Two school teachers were able to create a set of math games to entice their students that learning maths is fun. So, the teachers decides to test the newly developed games during class.
For a period of two weeks, one of the teachers convinced all her students and they played the maths game. The second teacher decides to use the normal teaching technique.
The results show that students who played the math games performed excellently on the test.
The two teachers could come to the conclusion that the games were key to improved performance in the test, but they cannot be 100% sure due to the lack of random assignment.
Action Research in the Classroom
- Type: Pre-Experimental Design
A teacher wants to find out if engaging in a small group activity will improve students’ skills on how to conduct a survey. Then, they organize and test the activity with some of their classes and closely observe the results.
The teacher may notice that the students respond very well to the activity. Since there were no comparison group of students who also learned how to conduct a survey, the teacher cannot be 100% sure that the activity is the best approach for teaching the subject.
Study on the Impact of an Advertisement
- Type: Pre-Experimental Design
An advertising firm decides to appoint two of its finest staff to develop an ad. The advert is about eating a brand’s breakfast product.
The team comes up with an idea to organize a skit where several characters are enjoying breakfast. They are also engaged in silly gestures and the background music was quite unusual.
The ad agency doesn’t want to spend money on the ad. The commercial is then shot with a low budget.
The firm shows the ad to a few individuals to observe their reactions. As the firm observed that the ad had a strong impact on viewers, they allocated a larger budget for the ad.
Economic Impact on Politics
- Type: Quasi-Experimental Design
An economic policy institute decides to access how effective the new policy is regarding the development of small businesses. Two cities in an underdeveloped country are identified by the institute.
The two cities are almost the same size. One of the two cities where the new policy was implemented indicated a higher growth of small businesses compared to the other city.
There may be some differences between the two cities which generally effects small business growth rather than the policy.
Gender and Mindfulness Apps Study
- Type: Quasi-Experimental Design
This is one of the examples of experimental design.
Researchers decided to conduct a study to find out between men and women who benefit from mindfulness.
The researcher recruited some office workers. The researcher split up the research sample into males and females. They asked the participants to use a mindfulness app for at least fifteen minutes daily.
By the end of three weeks, the researchers handed out a questionnaire that measures stress to all participants. They also measured stress hormones.
The result of the experiment shows that women responded better to the apps compared to the males. The women also showed lower stress levels.
However, the researchers cannot conclude that women respond better to the apps than men, since they could not randomly appoint participants to gender.
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Clinical Trials
- Type: True-Experimental Design
True experiments are sometimes used by medical researchers to test the effectiveness of different treatment regimens.
For example, people are randomly selected from the public to partake in research on the effects of medications on heart diseases.
They randomly assign participants to get the medications or not. All participants will be contacted after three months and given a heart disease test.
The results of the experiment indicated that individuals who received medications had lower levels of heart disease compared to those who did not.
Case Study
- Type: Pre-Experimental Design
A medical doctor thinks that certain rare medical illnesses can be treated with the use of an old treatment regimen.
Never for once has the treatment been used in this way. The medical doctor decides to apply the treatment to two patients diagnosed with the illness.
After a few weeks, they noticed that the treatment is not having any effect on the illness, so the medical doctor decides not to continue the treatment.
Fertilizer and Plant Growth Study
- Type: Pre-Experimental Design
A farmer decides to explore various combinations of nutrients for plant growth. The farmer decides to use fertilizer on some small plants in the lab rather than spending money and time applying several mixes to the soil.
After many weeks, the plants are growing as they should, producing dense branching. The farmer shows the results to her friends and they all concluded that further testing is required.
Parenting Styles and Academic Performance
- Type: Quasi-Experimental Design
Psychologists are eager to clearly understand how children’s academic performance is affected by parenting styles.
The psychologists identified a large group of parents practising one of the four parenting styles which are authoritative, permissive, authoritarian, and neglectful.
After a thorough review, the researchers found out that children raised with the authoritative style had better grades compared to the other three.
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Sport Nutrition Bars Study
- Type: True-Experimental Design
A company decides to test how effective its sports nutrition bars are by recruiting college students to partake in their experiment.
The college students were assigned to control conditions or treatment condition. The students in the treatment condition ate two nutrition bars, while those in the control condition also ate two similar nutrition bars with no nutritional value.
After the college students consumed the nutrition bars, they were allowed to run on a treadmill for fifteen minutes.
Participants that ate the nutrition bars ran faster on the treadmill. Their breathing was normal and they never complained of feeling too exhausted compared to participants who ate the non-nutritious bars.
Reading Comprehension and Lighting Study
- Type: True-Experimental Design
The different wavelengths of light will likely affect intellectual processing. A researcher selected several college students and asked them to read a history chapter in one of the 3 lighting conditions (natural sunlight, standard fluorescent light, and artificial light).
After reading the chapter, the college students sat for the same examination. After a thorough review, the researchers discovered that students who read with natural sunlight had a better score on the test.
The next best-scored students were those who read with yellow lights, followed by the fluorescent light. The researchers concluded that natural light enhances reading comprehension.
Conclusion
Experimental design is a central feature of the scientific method and it involves evaluating an independent variable against a dependent variable.
A common example of experimental design is a clinical trial that involves several research participants organized into control and treatment groups.
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References
- HelpfulProfessor: 15 Experimental Design Examples
- T Lundstedt et al 1998: Experimental design and optimization
- MI Rodrigues, AF Iemma – 2014: Experimental design and process optimization
- Study.com: Experimental Design Process
- SimlyPsychology: Experimental Design: Types, Examples & Methods
- D Faller, U Klingmüller, J Timmer – Simulation, 2003 Simulation methods for optimal experimental design in systems biology
