Investigation and Discrimination of Ballpoint Pen Inks by Analytical Techniques and Chemometrics

Table 4

The calculations for the number of clusters and DP for each cluster achieved from UV/Vis spectroscopy.

UV/Vis spectroscopy	ID of cluster	No. of ballpoint samples in cluster	Samples in cluster	Nondiscriminating sample pairs in cluster	Total no. of sample pairs	No. of discriminating sample pairs	DP	Average DP (for 2 clusters)
Blue	1	8	1, 3, 4, 5, 6, 9, 14, 18	—	28	28	1	0.98
	2	12	2, 7, 8, 10, 11, 12, 13, 15, 16, 17, 19, 20	12, 13 and 19, 20	66	64	0.969
Black	1	8	1, 2, 4, 5, 6,7, 11, 13	—	28	28	1	0.99
	2	11	3, 8, 9, 10, 12, 14, 15, 16, 17, 18, 19	12, 14	55	54	0.98
Green	1	4	1, 3, 4, 6	—	6	6	1	1
	2	2	2, 5	—	1	1	1
Red	1	5	1, 3, 4, 7, 8	—	10	10	1	1
	2	3	2, 5, 6	—	3	3	1

UV/Vis: ultraviolet visible spectroscopy; DP: discriminating power.