correlation coefficient;  fitting;  Superiority;  Regression

In experimental data processing, the magnitude of the correlation coefficient is often used to express the criterion of linear fit. Through experimental illustration analysis and research, a good correlation coefficient does not necessarily mean a good straight-line fitting result, and a good linear fitting of experimental results does not necessarily mean a large correlation coefficient, indicating that the correlation coefficient should not be used as a criterion for the goodness-of-fit of experimental results. It is only meaningful if it is a regression coefficient, or when there is a variable that cannot be measured on a fixed scale.