Calibration Set (36) R2 = 0.98724 RPD = 8.8525 RMSEC = 0.3308 SEC = 0.3355 Bias = 0.0000 Test Set (29) R2 = 0.98792 RPD = 9.0970 RMSEP = 0.3249 SEP = 0.3304 Bias = 0.0140
What does that mean?The data is splited into 3 independent sets.
The “Reference vs. Predicted” plot shows the 3 sets in different colors.
The Calibration Set (CSet) to build the calibration and
the Validation Set (VSet) used to determine the calibration parameters and
the Test Set (TSet) used to measure the calibration performance.
The statistical values are listed for the CSet and the TSet as follow:
Calibration Set (the number of spectra per set)
R = Poor 0.0 - 1.0 Excellent correlation coefficient or coefficient of correlation, how close the data are to the fitted regression line. R2 = Poor 0.0 - 1.0 Excellent R-squared value or coefficient of determination. R2 = R * R : determination (R2) is the square of the correlation (R). RPD = Degrees of merit for the Ratio of Performance Deviation (RPD) to the application of NIR spectroscopy. RPD value Rating NIR Application 0.0 - 1.99 Very poor Not recommended 2.0 - 2.49 Poor Rough screening 2.5 - 2.99 Fair Screening 3.0 - 3.49 Good Quality control 3.5 - 4.09 Very good Process control 4.1 - oo Excellent Any application RMSEC = Accuracy = total error : Root Mean Square Error of Calibration SEC = Precision = random error : Standard Error of Calibration = Sdev(x-y): as small as possible (around the standard deviation of the reference method) Bias = Trueness = systematic error : by definition 0 for the calibration.
Test Set (the number of spectra per set)
R = Correlation , as above R2 = Determination , as above RPD = Applicativity , as above RMSEP = Accuracy = total error : Root Mean Square Error of Prediction SEP = Precision = random error : Standard Error of Prediction = Sdev(x-y) : as small as possible (around the standard deviation of the reference method) Bias = Trueness = systematic error : around 0
look at Test Set RPD : for rating and applicativity and Test Set RMSEP : for comparison with reference method