Experimental and Observational Designs Section
Research studies are often classified in terms of their designs. Here, we will make the distinction between experimental and observational research designs.
- Experimental Research Design
A study in which the researcher manipulates the treatments (i.e., level of the explanatory variable) received by subjects and collects data; also known as a scientific study
- Observational Research Design
A study in which the researcher collects data without performing any manipulations; also known as a non-experimental study
Example: Caffeinated Coffee Studies Section
An organization wants to know if drinking caffeinated coffee causes hyperactivity in college students. To test their research question, they select a sample of college students and give them a survey concerning their intake of caffeinated coffee and their hyperactivity levels. This is an observational study because the researchers are not making any manipulations. They are observing what is happening without intervening. This is not an experiment because no treatment was imposed by the researchers.
Another organization also wants to know if drinking caffeinated coffee causes hyperactivity in college students. They design a different study. They select a random sample of college students and randomly assign them to drink coffee with or without caffeine. The researchers observe the students' behaviors. This is an experimental study because the researchers are manipulating the treatment that each participant receives.
Choosing a Research Study Design Section
Usually, if there is an option available, experimental studies are preferred over observational studies. Later in this lesson you will learn about randomization, placebos, and blinding, which can all be built into experimental designs to strengthen the conclusions that can be made.
There are times when an experimental design is not possible. If the independent variable is naturally occurring, it may not be possible for a researcher to manipulate it. For example, race, ethnicity, birthplace, age, gender identity, and biological sex are all variables that cannot be randomly assigned to different cases.
On Your Own Section
A team of researchers want to know if Advil or Tylenol is more effective.
Think about the following data collection methods, then click on the method to compare your answers.