# Observational Study in Statistics: Definition & Examples

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Instructor: Laura Pennington

Laura has taught collegiate mathematics and holds a master's degree in pure mathematics.

In this lesson, we will learn what an observational study is and look at some examples of such a study. We will also discuss some of the advantages and disadvantages of this type of study.

## What Is an Observational Study?

Statistics is the process of collecting data about a group of objects to draw conclusions about populations of those objects. For example, a statistician may take a sample group of workers from company XYZ and have them rate their job satisfaction with the company. Based on the results of that sample, the statistician can make educated assumptions about all of the employees of company XYZ and their job satisfaction.

Statistics involves a lot of studies, experiments, and data collection. One such type of study is the observational study. An observational study is a study in which the researcher simply observes the subjects without interfering. That is, the researcher has no control over any treatments the subjects may be given or which groups the subjects may be separated into, etc. They just observe the subjects and record data based on their observations.

## Examples of Observational Studies

As we said, an observational study is one in which the researcher doesn't manipulate anything. Let's consider some examples of such a study.

A very simple example would be a survey of some sort. Consider someone on the busy street of a New York neighborhood asking random people that pass by how many pets they have, then taking this data and using it to decide if there should be more pet food stores in that area. This is an observational study, because the researcher is simply observing the answers of the survey without influencing the outcome in any way.

Another example of an observational study would be if a researcher was trying to determine the effects that eating strictly organic foods has on overall health. The researcher finds 200 individuals, where 100 of them have eaten organically for the past three years, and the other 100 haven't eaten organically in the past three years. They then give each subject an overall health assessment. Lastly, they analyze the data and use it to draw conclusions on how eating organically can affect one's overall health. This is an observational study, because the researcher hasn't done anything other than observe the individuals in the study.

## Non-Example of an Observational Study

Consider our organic foods example of an observational study. Another form of this study could consist of the researcher gathering 200 random people that do not eat organically, and then having 100 of those people eat organically for the next three years and 100 of those people not eat organically for the next three years, and observing the effects on their overall health after those three years.

Notice that, in this scenario, the researcher is influencing the subjects by having them switch their eating habits, which would be considered the treatment in this case. If the study is conducted this way, then it's no longer an observational study, as the researcher has influence on the study, whereas in the other scenario, the researcher is just observing individuals without changing or influencing them.

There are advantages and disadvantages to any type of study. First, let's consider some of the advantages of an observational study:

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