Aaron wants to study the association between sleep deprivation and the number of hours spent on computer every day. He is not keen to establish causation, but would like to determine whether and how the increase or decrease in one variable is associated with the increase or decrease in the other variable. Which of the following research methods is likely to be most effective for Aaron’s study?
1. experimental research
2. correlational research
3. case study
4. survey

Correlational research intends to understand the relationship between two or more variables in a study. For example, an article named "Listening to classical music might increase your concentration" is likely based on correlational research.

As the passage states, correlational studies do not seek to find a cause-effect relationship. The study in the example might reveal that sleep influences a person's use of a computer (or the other way around), but that does not mean one is the only direct cause for the other.