A correlation refers to a relationship between two variables. Correlations can be strong or weak and positive or negative. Sometimes, there is no correlation.

Verywell / Brianna Gilmartin

What Correlation Means

There are three possible outcomes of a correlation study: a positive correlation, a negative correlation, or no correlation. Researchers can present the results using a numerical value called the correlation coefficient.

  • Positive correlations: Both variables increase or decrease at the same time. A correlation coefficient close to +1.00 indicates a strong positive correlation.
  • Negative correlations: As the amount of one variable increases, the other decreases (and vice versa). A correlation coefficient close to -1.00 indicates a strong negative correlation.
  • No correlation: There is no relationship between the two variables. A correlation coefficient of 0 indicates no correlation.

What Is a Correlation Coefficient?

The correlation coefficient is a measure of the correlation strength. It can range from –1.00 (negative) to +1.00 (positive). A correlation coefficient of 0 indicates no correlation.

How Correlational Studies Work

Correlational studies are a type of research often used in psychology, as well as other fields like medicine. Correlational research is a preliminary way to gather information about a topic. The method is also useful if researchers are unable to perform an experiment.

Researchers use correlations to see if a relationship between two or more variables exists, but the variables themselves are not under the control of the researchers.

While correlational research can demonstrate a relationship between variables, it cannot prove that changing one variable will change another. In other words, correlational studies cannot prove cause-and-effect relationships.

Types of Correlational Research

There are three types of correlational research: naturalistic observation, the survey method, and archival research. Each type has its own purpose, as well as its pros and cons.

Naturalistic Observation

The naturalistic observation method involves observing and recording variables of interest in a natural setting without interference or manipulation.


  • Can inspire ideas for further research

  • Option if lab experiment not available

  • View variables in natural setting


  • Can be time-consuming and expensive

  • Extraneous variables cant be controlled

  • No scientific control of variables

  • Subjects might behave differently if aware of being observed

This method is well-suited to studies where researchers want to see how variables behave in their natural setting or state. Inspiration can then be drawn from the observations to inform future avenues of research.

In some cases, it might be the only method available to researchers; for example, if lab experimentation would be precluded by access, resources, or ethics. It might be preferable to not being able to conduct research at all, but the method can be costly and usually takes a lot of time.

Naturalistic observation presents several challenges for researchers. For one, it does not allow them to control or influence the variables in any way nor can they change any possible external variables.

However, this does not mean that researchers will get reliable data from watching the variables, or that the information they gather will be free from bias.

For example, study subjects might act differently if they know that they are being watched. The researchers might not be aware that the behavior that they are observing is not necessarily the subjects natural state (i.e., how they would act if they did not know they were being watched).

Researchers also need to be aware of their biases, which can affect the observation and interpretation of a subjects behavior.

The Survey Method

Surveys and questionnaires are some of the most common methods used for psychological research. The survey method involves having a random sample of participants complete a survey, test, or questionnaire related to the variables of interest. Random sampling is vital to the generalizability of a surveys results.


  • Cheap, easy, and fast

  • Can collect large amounts of data in a short amount of time

  • Flexible


  • Results can be affected by poor survey questions

  • Results can be affected by unrepresentative sample

  • Outcomes can be affected by participants

If researchers need to gather a large amount of data in a short period of time, a survey is likely to be the fastest, easiest, and cheapest option.

Its also a flexible method because it lets researchers create data-gathering tools that will help ensure they get the information they need (survey responses) from all the sources they want to use (a random sample of participants taking the survey).

Survey data might be cost-efficient and easy to get, but it has its downsides. For one, the data is not always reliable—particularly if the survey questions are poorly written or the overall design or delivery is weak. Data is also affected by specific faults, such as unrepresented or underrepresented samples.

The use of surveys relies on participants to provide useful data. Researchers need to be aware of the specific factors related to the people taking the survey that will affect its outcome.

For example, some people might struggle to understand the questions. A person might answer a particular way to try to please the researchers or to try to control how the researchers perceive them (such as trying to make themselves look better).

Sometimes, respondents might not even realize that their answers are incorrect or misleading because of mistaken memories.

Archival Research

Many areas of psychological research benefit from analyzing studies that were conducted long ago by other researchers, as well as reviewing historical records and case studies.

For example, in an experiment known as The Irritable Heart, researchers used digitalized records containing information on American Civil War veterans to learn more about post-traumatic stress disorder (PTSD).


  • Large amount of data

  • Can be less expensive

  • Researchers cannot change participant behavior


  • Can be unreliable

  • Information might be missing

  • No control over data collection methods

Using records, databases, and libraries that are publically accessible or accessible through their institution can help researchers who might not have a lot of money to support their research efforts.

Free and low-cost resources are available to researchers at all levels through academic institutions, museums, and data repositories around the world.

Another potential benefit is that these sources often provide an enormous amount of data that was collected over a very long period of time, which can give researchers a way to view trends, relationships, and outcomes related to their research.

While the inability to change variables can be a disadvantage of some methods, it can be a benefit of archival research. That said, using historical records or information that was collected a long time ago also presents challenges. For one, important information might be missing or incomplete and some aspects of older studies might not be useful to researchers in a modern context.

A primary issue with archival research is reliability. When reviewing old research, little information might be available about who conducted the research, how a study was designed, who participated in the research, as well as how data was collected and interpreted.

Researchers can also be presented with ethical quandaries—for example, should modern researchers use data from studies that were conducted unethically or with questionable ethics?

Limitations of Correlational Studies

Youve probably heard the phrase, correlation does not equal causation. This means that while correlational research can suggest that there is a relationship between two variables, it cannot prove that one variable will change another.

For example, researchers might perform a correlational study that suggests there is a relationship between academic success and a persons self-esteem. However, the study cannot show that academic success changes a persons self-esteem.

To determine why the relationship exists, researchers would need to consider and experiment with other variables, such as the subjects social relationships, cognitive abilities, personality, and socioeconomic status.

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