Table 4.
Simple Regression Analysis on Radial Reduction of Specimens (Y) and Vessel Diameter Reduction in Central Zone

Species	Independent variable	R-squared	Adjusted R-squared	Constant	t-statistic	P-value
Andong	Y-intercept	0.953	0.942	-0.566	-0.419	6.96×10-1
	Vessel (X1)			0.645	9.043	8.28×10-4
Hitam	Y-intercept	0.997	0.996	2.392	5.077	1.47×10-2
	Vessel (X1)			1.898	31.138	7.27×10-5
Tali	Y-intercept	0.913	0.884	1.222	0.543	6.24×10-1
	Vessel (X1)			0.491	5.609	1.11×10-2
Kuning	Y-intercept	0.951	0.939	-0.421	-0.288	7.87×10-1
	Vessel (X1)			0.977	8.823	9.10×10-5
Ampel	Y-intercept	0.907	0.876	4.769	1.688	1.89×10-1
	Vessel (X1)			0.763	5.418	1.23×10-2
Betung	Y-intercept	0.964	0.951	-0.212	-0.107	9.21×10-1
	Vessel (X1)			1.381	8.904	2.98×10-3