7 Types of Observational Studies (With Examples)

Observational studies can help statisticians, scientists, psychologists, business market analysts and other professionals understand natural behaviors or phenomena. The various types of observational studies all offer distinct advantages to individuals or organizations aiming to conduct research. If you work in any field where research is necessary, you may encounter the different types of observational studies and need to understand how they work. 

In this article, we discuss what observational studies are, some examples of observational studies, the seven main types of observational studies and how observational studies compare to experimental studies.

What are observational studies?

Observational studies are research processes where individuals or organizations examine something without manipulating it. Most observational studies today involve observing people or animals, but researchers might also observe natural phenomena, such as the weather or volcanoes. Researchers might study one or more factors related to their chosen subject, such as a characteristic or behavior. If a researcher has chosen observational studies, they do not attempt to change or influence the factors under observation.

Related: 6 Types of Research Studies (Advantages and Disadvantages)

What are some examples of observational studies?

Observational studies can encompass many fields and factors. A researcher conducting observational studies might observe one or more factors related to:

• Animals in their natural environment

• Human use of a specific company's products or services

• Natural disasters such as tornadoes, hurricanes or tsunamis

• Humans using technology

• Erosion or natural movement of land

• Human behavior in a particular setting, such as a coffee shop or religious gathering

• Animals at a zoo or wildlife reserve

• Humans being screened for a particular medical condition, such as cancer

• Stars, planets and other astronomical phenomena

• Humans belonging to a particular group, such as gender or nationality

Related: What Is the Scientific Method? 7 Steps to Test Conclusions

7 types of observational studies

There are seven types of observational studies. Researchers might choose to use one type of observational study or combine any of these multiple observational study approaches:

1. Cross-sectional studies

Cross-sectional studies happen when researchers observe their chosen subject at one particular point in time. This method is one of the easier types of observational studies, as it does not require collecting and analyzing data multiple times. A scientist performing a cross-sectional study, for example, might look at how frequently people from a certain demographic, such as age group, contract a particular disease.

Related: Cross-Sectional Study Examples, Types and Benefits

2. Case-control studies

Case-control studies involve comparing two or more groups of participants or phenomena. One of these groups is the control group and the others are the treatment groups. The only difference between the control and treatment groups is the factor under observation. Comparing a control group with the treatment group helps make sure that the results of the study are valid.

For example, imagine that you want to study the effects of caffeine on sleep habits. Your treatment group would be people who regularly drink caffeine. Your control group would match your treatment group in demographics, such as age and gender, but wouldn’t regularly consume caffeine. Studying the sleep habits of both groups could help you understand how caffeine affects sleep habits.

Related: What Is a Case Study? Definition, Elements and 15 Examples

3. Cohort studies

A cohort refers to a group of people with a common trait. This common trait might be based on a demographic or behavior. Researchers who choose a cohort study method only observe people who share a particular characteristic. Researchers then observe what happens within the cohort to analyze if certain traits within the cohort influence variable responses. For example, scientists using a cohort study might study people all born during the same week from a particular region. These scientists would observe multiple years’ worth of differences in the cohort's behaviors, such as diet, social interactions or habits.

Related: Types of Research Methods (Definition and Best Practices)

4. Naturalistic observation

Naturalistic observation means that scientists study human or animal behavior in the natural environment where those behaviors occur. Naturalistic observation is a type of field research, meaning that researchers collect their data outside of a laboratory or clinical setting. Researchers using naturalistic observation try to integrate themselves with the environment as much as possible so that participants do not know they are being observed and subsequently alter their natural behaviors. Many zoologists, or scientists who study animal behaviors, use a naturalistic approach to their research.

Related: Q&A: What Are the Main Scientific Fields of Study?

5. Participant observation

Like naturalistic observation, participant observation involves studying behaviors in their natural environment. However, unlike naturalistic observation, researchers become active in their study during participant observation. Researchers often choose participant observation when they can only gather certain data by assimilating or taking on roles that resemble those in the natural environment. For example, a scientist wanting to know more about behaviors in a rehabilitation facility could enroll themselves as a patient. Business market analysts might also use participant observation to assess public use or knowledge of a particular product or service.

Related: 20 Types of Research Designs

6. Structured observation

Unlike participant and naturalistic observation, structured observation does not involve studying participants in their natural environment. Instead, scientists using structured observation study participants in a more constructed or controlled environment. The structured environment might be a laboratory, clinic or research facility. However, the structured environment could also be a natural environment altered in some way by the researchers. For example, business market analysts might give participants in an office environment a certain task to perform or a certain product to use.

Related: FAQ: What Is a Cross-Sectional Analysis? (Plus Example)

7. Longitudinal studies

Longitudinal studies involve observing the same factors over distinct periods of time. The time intervals of the study might be short, such as observing participants at multiple points over the course of an hour. These time intervals could also span longer periods, such as months or even years. For example, scientists might use longitudinal studies to observe developmental growth in babies and children. Market analysts could also use longitudinal studies to track public awareness of a business's products or services over a year or longer.

Related: Types of Research: Definitions and Examples

Observational studies vs. experimental studies

Experimental studies are another category of scientific studies. Here are the fundamental similarities and differences between observational studies and experimental studies:

Influencing results

The primary difference between experimental and observational studies is that experimental studies attempt to affect the scientific results. During an experimental study, scientists influence or intervene in the study to see what effect their manipulation has.

For example, scientists use an experimental study design to figure out if a new medical treatment can help cure or minimize the symptoms of a particular health condition. In this scenario, all participants have a medical issue, but scientists divide the participants into two distinct groups. One group receives the new treatment while the other group receives a placebo, or a substance that does not affect their health. Scientists then evaluate if the group receiving the new treatment saw significant improvements in their medical condition compared to the control group.

Related: Designing an Experiment: A How-To Guide

Assigning methods

In an experimental study, researchers typically assign participants a specific task, treatment or method of doing something. In an observational study, researchers study how participants perform certain behaviors or activities without telling them what methods or behaviors to choose. For example, if a scientist wants to study how the amount of water humans drink affects their diets, they might choose an observational study. In the study, they would evaluate the existing diets of participants who already drink different amounts of water.

The scientist could also choose an experimental design for the same study. In this type of study, the scientist would sort the participants into distinct groups and assign each group a certain amount of water to drink each day. The scientist would then analyze if there were any significant dietary changes among the study groups.

Related: Experimental vs. Observational Study: 5 Primary Differences

Constructing an environment

Experimental studies typically create an environment with one or more controlled or manipulated elements. An experimental study often occurs in a laboratory or other structured environment. Participants in an experimental study also typically need to perform a specific task or undergo a specific treatment. Observational studies, however, focus on studying behaviors in natural environments uncontrolled by researchers.

Finding participants

Both observational and experimental studies often use random sampling methods to find participants. Random sampling is used to gather a small segment of a particular population that represents that population as a whole. For example, if a scientist wants to study a certain behavior in children, they might use a random sampling method to find participants for the study, whether that study is observational or experimental.

Determining causal relationships

Experimental studies are typically more accurate in proving causal relationships. A causal relationship means that one factor directly creates or influences the second factor. In an observational study, it is more likely for a confounding variable, or an unmeasured and unpredicted factor, to influence the data.

Continuing with the drinking water example, the best approach to this type of study would likely be an experimental study. If the scientist chooses an observational study, there might be confounding variables, such as sleep or exercise habits, that also affect diet in addition to the amount of drinking water. Although these confounding variables might still be present in an experimental study design, confounding variables are likely reduced because the scientist is manipulating the water consumption of participants and then evaluating their dietary changes.

Costs

Observational studies typically are not as expensive as experimental studies. Creating an environment with more controls or manipulations typically creates a more costly study. Because observational studies are less expensive, they can often run for longer periods of time. It’s easier for scientists to ask participants to answer some questions every year than it is to replicate annually the exact environment and controls of a particular experimental study.