A correlation coefficient is a statistical test to evaluate the degree and the direction of linear correlation between two variables. The Pearson correlation coefficient, denoted by 'r,' is commonly used. Here, 'n' represents the total number of observations. The value of 'r' calculated in a calibration curve ranges from −1 to +1. While a value closer to +1 indicates a stronger positive linear correlation between the two variables, a value closer to −1 infers a stronger negative linear correlation, and a zero value affirms no linear correlation. The coefficient of determination denoted by 'r2' or 'R2' is a better statistical test that tells the reliability of the mathematical model in explaining the variation in the data. The R2 value ranges from 0 to 1. A value of 0.999 indicates an excellent fit.