How to calculate the correlation coefficient r of two variables?

The formula for calculating the correlation coefficient r is:

The absolute value of r is between 0 and 1. Generally speaking, the closer R is to 1, the stronger the correlation between X and Y. Conversely, the closer R is to 0, the weaker the correlation between X and Y. It is generally believed that:

Extended data:

It should be noted that Pearson correlation coefficient is not the only correlation coefficient, but the most common correlation coefficient. The following explanation is aimed at Pearson correlation coefficient.

According to the different characteristics of related phenomena, the names of their statistical indicators are also different. For example, the statistical index reflecting the linear correlation between two variables is called correlation coefficient (the square of correlation coefficient is called judgment coefficient); The statistical indexes reflecting the curve correlation between two variables are called nonlinear correlation coefficient and nonlinear judgment coefficient. The statistical indexes reflecting multivariate linear correlation are called complex correlation coefficient and complex judgment coefficient.