Experiments vs Observational Studies: Definition, Differences & Examples

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• 0:00 Conducting Research
• 1:45 Observational Studies
• 3:25 Experiments
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Lesson Transcript
Instructor: Cathryn Jackson

Cat has taught a variety of subjects, including communications, mathematics, and technology. Cat has a master's degree in education and is currently working on her Ph.D.

There are different ways to collect data for research. In this lesson, you will learn about collecting data through observational studies and experiments and the differences between each.

Conducting Research

Emily has been doing research for her psychology class. She is studying the academic successes of ballet dancers. She wants to know if ballet dancers have higher grades than peers who do not study dance. She can approach this research a couple of different ways. Emily can either conduct an experimental or an observational study.

In this lesson, you will learn about experimental and observational studies and how they both use statistics. First, you will need to understand two types of variables that occur in both - response and explanatory - as well as the more familiar independent and dependent variables.

A response variable is the observed variable, or variable in question. In Emily's study, the grades, or academic success, would be the response variable. This is similar to a dependent variable, which is a condition or piece of data in an experiment that is controlled or influenced by an outside factor, most often the independent variable. These concepts are similar, but not the same. We will look at how each are used in experimental and observational studies later in this lesson. First, let's finish reviewing the other important terms.

An explanatory variable is a variable, or set of variables, that can influence the response variable. In Emily's case, she believes that ballet is the explanation for increased academic success. This is similar to an independent variable, which is a condition or piece of data in an experiment that can be controlled or changed. The difference between explanatory variables and independent variables is that explanatory variables can't always be controlled or changed.

Now that you understand explanatory, independent, response and dependent variables, let's discuss observational studies.

Observational Studies

Emily has decided to conduct an observational study to collect data on ballet dancers and their grades in school. An observational study is a study where researchers simply collect data based on what is seen and heard and infer based on the data collected. Researchers should not interfere with the subjects or variables in any way. Emily will collect data by conducting a survey, asking each dancer his or her level of ability, number of hours spent training per week, GPA in school and averages in each class. Once Emily collects this data, she can use the data to develop a conclusion.

Two things are required of an observational study. First, the variables must be observed and the data must be collected through observation. A researcher can't add in any extra information, or guesses. All of the information must be evidence in the observational study. Second, the researcher can only observe, they cannot interfere with the study in any way.

Observational studies have explanatory and response variables only. Because the researcher cannot interfere with the study, there cannot be any independent nor dependent variables. Remember, an independent variable is something that is controlled in the study. The researcher has no control of the variables in an observational study. Emily can use an observational study to make comparisons between dancers and non-dancers for her class.

What if you need a study that you can control? What if you need independent and dependent variables? Or what if you need to find cause and effect? It is better studied using an experiment.

Experiments

Emily decides to conduct an experiment to find if dance is the cause of better grades in students. She uses the students in a local middle school for her experiment. She uses two groups of middle school students that have never taken a dance class before. She has one group take one dance class a day, and the other group takes no classes. Each week over the semester, she records their progress in class.

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