Table 4. Parameter estimates for equations in Table 2 by species using 6th national forest inventory. All estimated parameters were significantly different from zero (p < 0.005). The result of optimal equation for each tree species were bold type.

Species	Parameters				Performance Criteria
	Model No.	a	b	c	R2	RMSE	MD	AMD	AIC
PD	1	28.939	0.010	0.583	0.432	2.693	-0.001	2.108	166,256
	2	35.330	0.054	0.634	0.432	2.693	-0.001	2.108	166,237
	3	2.926	-10.687		0.415	2.733	0.014	2.136	167,273
	4	264.080	5.244	0.164	0.432	2.692	-0.001	2.108	166,250
	5	0.007	1.951	23.563	0.432	2.693	-0.001	2.108	166,247
	6	27.910	-34.247	15.502	0.431	2.695	0.000	2.110	166,311
	7	52.426	0.035	0.662	0.432	2.693	-0.001	2.108	166,247
LK	1	25.287	0.082	1.805	0.611	3.288	0.001	2.583	23,313
	2	24.721	0.019	1.382	0.611	3.288	-0.002	2.584	23,314
	3	3.499	-13.340		0.610	3.295	-0.001	2.588	23,329
	4	31.637	15.861	1.086	0.610	3.294	0.003	2.587	23,329
	5	0.088	0.302	26.261	0.611	3.288	-0.002	2.583	23,315
	6	32.766	-12.750	-0.384	0.610	3.294	0.002	2.587	23,331
	7	27.766	0.007	1.820	0.611	3.289	0.002	2.583	23,316
QV	1	19.043	0.057	1.082	0.561	2.324	-0.001	1.821	61,580
	2	18.997	0.047	1.046	0.561	2.324	-0.001	1.821	61,581
	3	3.075	-10.748		0.559	2.330	0.007	1.826	61,655
	4	27.990	6.300	0.690	0.561	2.323	0.000	1.821	61,572
	5	0.058	0.895	20.183	0.561	2.324	-0.001	1.821	61,581
	6	24.090	-14.992	3.179	0.561	2.323	0.000	1.820	61,571
	7	22.471	0.027	1.285	0.561	2.323	-0.001	1.821	61,573
QM	1	14.695	0.086	1.221	0.498	2.153	-0.001	1.680	78,888
	2	14.618	0.056	1.113	0.498	2.153	-0.001	1.680	78,890
	3	2.865	-8.560		0.498	2.154	0.000	1.679	78,895
	4	17.724	8.293	0.988	0.498	2.154	0.000	1.679	78,897
	5	0.088	0.724	15.876	0.498	2.153	-0.001	1.680	78,890
	6	17.741	-8.716	0.219	0.498	2.154	0.000	1.679	78,897
	7	16.193	0.026	1.521	0.498	2.153	0.000	1.679	78,887