What does correlation measure in psychological research?

Correlation measures the strength and direction of the relationship between two variables. In psychological research, when researchers use correlation, they are often interested in understanding how two variables are related to one another, whether positively or negatively. A positive correlation indicates that as one variable increases, the other also tends to increase, while a negative correlation suggests that as one variable increases, the other tends to decrease. The strength of the correlation can range from -1 to +1, with values closer to these extremes indicating a stronger relationship. This concept is foundational in psychology, as it helps researchers identify patterns and make predictions about behaviors and outcomes based on relationships observed in data.

The other options reflect different aspects of research methodologies. For instance, establishing cause-and-effect relationships pertains more to experimental designs rather than correlation, as correlation alone does not imply causation. The variance of a single variable is a statistical concept that deals with how much a variable fluctuates and does not relate to the relationship between two separate variables. Lastly, the differences between control and experimental groups are typically assessed through comparative analyses or experimental designs, focusing on how treatment or conditions affect outcomes, rather than examining a relationship between two separate variables.