In a linear calibration curve, there is a value called the calibration coefficient, denoted by 'r,' which measures the strength and the direction of association between two variables. The correlation coefficient value ranges from −1 to +1. A value of +1 indicates a perfect positive linear correlation, −1 denotes a perfect negative correlation, and 0 implies no correlation between the two variables. A positive correlation value establishes that as one variable increases, the other increases, and vice versa. On the contrary, a negative correlation value indicates that as one variable increases, the other variable decreases, and vice versa. Squaring the correlation coefficient results in the coefficient of determination, denoted by 'r²' or 'R²'. This value ranges from 0 to 1. A value closer to 1, such as 0.999, indicates an excellent fit, whereas a value close to 0 indicates a poor fit.