Which method is typically used to determine the strength of a relationship between variables?

Correlation analysis is the method specifically used to determine the strength and direction of a relationship between two variables. It evaluates how closely related the variables are and whether they tend to increase or decrease together. This method yields a correlation coefficient, which is a numerical value that ranges from -1 to 1. A value close to 1 indicates a strong positive correlation, while a value close to -1 indicates a strong negative correlation. A value around 0 suggests no correlation.

In contrast, random sampling is a technique used to select a representative sample from a population, which is critical for ensuring the generalizability of research findings but does not measure relationships. The experimental method involves manipulating one variable to see how it affects another, aiming to establish causation rather than simply assessing the strength of a relationship. Longitudinal research tracks variables over an extended period, allowing for the assessment of changes and trends, but it does not specifically measure the strength of the relationship between variables at a single point in time.