What does a correlation coefficient (r) represent?

A correlation coefficient (r) specifically quantifies the degree of association between two variables. This statistical measure indicates how closely two variables are related and how one may predict the other. The value of r ranges from -1 to +1, where values close to 1 or -1 imply a strong relationship—positive or negative, respectively—while a value around 0 indicates little to no relationship. This concept is integral in fields such as kinesiology, as it allows researchers and practitioners to understand the interactions between different physical performance metrics, health outcomes, and training variables.

In contrast, the other choices focus on specific physical traits or physiological attributes rather than the relationship between variables. For instance, strength of muscle contractions or endurance levels are measurements of physical performance rather than statistical associations, and flexibility pertains to a physical characteristic rather than a statistical relationship.