Comparison of estimators of variance for forest inventories with systematic sampling - results from artificial populations

Forest Ecosystems

Table 4 Estimated variances in populations with a near zero autocorrelation and a strong, a moderate, and a weak global linear trend. All table entries are means across 30 realizations of a super-population and the K possible samples for a given sampling interval (d). Variances in parentheses are relative variances with the DES variance fixed at 100. τ_{i, j} is the trend component for unit in row i and column j (i, j = 0.5, 1.5 …, 239.5)

Trend	Trend variance (%)	Site effect variance(%)	Sample size (units)	Sample interval (units)	Variance estimator × 10³
Trend	Trend variance (%)	Site effect variance(%)	Sample size (units)	Sample interval (units)	DES	SRS	MAT	SDR	RIP	DOR
Strong τ_{i, j} = (i + j − 241)/120	45	2	400	12	1.51 (100)	2.50 (166)	1.46 (97)	1.47 (98)	1.84 (122)	1.48 (98)
			1600	6	0.29 (100)	0.63 (214)	0.36 (124)	0.37 (125)	0.36 (124)	0.37 (126)
Moderate τ_{i, j} = (i + j − 241)/240	14	2	400	12	2.12 (100)	2.49 (117)	2.09 (98)	2.09 (98)	2.28 (107)	2.03 (96)
			1600	6	0.42 (100)	0.62 (149)	0.52 (123)	0.52 (124)	0.52 (124)	0.52 (123)
Weak τ_{i, j} = (i + j − 241)/480	4	2	400	12	2.36 (100)	2.49 (105)	2.34 (99)	2.33 (99)	2.41 (102)	2.25 (95)
			1600	6	0.47 (100)	0.62 (133)	0.58 (123)	0.58 (123)	0.58 (122)	0.57 (122)