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Table 2 PLS calibration and validation parameters for regression models for date, pH, DP and zero-span tensile strength index (TSI); N—number of samples

From: Characterisation of 19th and 20th century Chinese paper

PLS model Calibration Validation
N RMSECV Factors R 2 Pre-processing N RMSEP R 2
Five sheets Date 112 21 6 0.6 SNV, MSC 33 24 0.53
Date post-1900 86 9 9 0.67 SNV, MSC 29 15 0.47
pH 135 0.5 8 0.66 MSC, S-Golay*, SNV 38 0.7 0.37
DP 63 370 8 0.84 SNV, MSC, S-Golay** 21 690 0.52
TSI 45 28 8 0.69 MSC, SNV, S-Golay*
One sheet Date 112 21 7 0.64 MSC, S-Golay*, SNV 33 31 0.3
Date post-1900 86 10 8 0.74 SNV, MSC, S-Golay* 29 13 0.41
pH 135 0.5 7 0.63 MSC, S-Golay*, SNV 38 0.7 0.4
DP 63 500 7 0.72 SNV, MSC, S-Golay* 21 720 0.55
TSI 45 30 8 0.63 MSC, SNV, S-Golay*
  1. Due to the low number of observations, independent validation was not carried out for TSI
  2. *First derivative, three-point smoothing, second order polynomial
  3. **Second derivative, three-point smoothing, second order polynomial