What is the numerical index that describes the relationships between two variables?

A) regression coefficient
B) chi index
C) correlation coefficient
D) psi index

The numerical index that describes the relationship between two variables is called the correlation coefficient. It measures the strength and direction of a linear relationship between two variables, ranging from -1 to 1. The closer the correlation coefficient is to 1, the stronger the positive relationship, while the closer it is to -1, the stronger the negative relationship. A correlation coefficient of 0 indicates no relationship between the variables.