Table 2.

Modified partial least-squares statistics of calibration and cross-validation for two calibration models developed using near-infrared reflectance spectroscopy (NIRS) for crude protein content (CP, in%) based on different sample sets and combinations of cowpea leaves from Eastern Africa

Model	N	Mean	SD	Min	Max	SECV	R2	G-H	RPD
Initial1	103	30.9	5.45	14.7	47.3	0.60	0.82	3.46	11.2
New	261	32.1	4.52	18.6	45.7	0.74	0.93	0.71	6.84

N, number of spectra in the calibration set; Mean, estimated by NIRS (expressed as CP, in %); SD, standard deviation; Min, lowest value of reliably estimating samples; Max, maximum value of reliably estimating samples; RPD, ratio performance deviation; SECV, standard error of cross-validation; R², determination coefficient of calibration; G-H, global-H value, where H is the Mahalanobis distance.

¹Initial calibration model (Tefera 2006) of 107 samples had four outliers removed.