Table 3.

Statistical outputs and performance parameters for segmented regression analysis modelling relationships between the precision of estimated means and sampling intensity (number of random samples/sampling grid). Response variables include Asiatic Garden beetle, Maladera formosae Brenske, larvae/0.25 m² (larval density), plant height (cm), root rating (1-5 nominal scale), above-ground biomass (g), and below-ground biomass (g). Breakpoint estimates represent the sampling intensity where diminishing returns in precision accrue with additional sampling effort. Precision was calculated as the average variance among the means estimated by 50 random draws at each level of sampling intensity (n = 1–63 or 1–47). True means represent estimates provided by sampling all cells in the 64- or 48-cell grid. Total area = 0.2 or 0.15 ha.

Field	Sampling Method	Response Variable	True Mean (± SE)	Precision Breakpoint (± SE)	df	t	P	R 2
1	Cup-cutter	Larval Density	13.0 ± 2.7	5.2 ± 0.2	59	−12.4	<0.001	0.91
2	Cup-cutter	Larval Density	5.5 ± 1.8	4.1 ± 0.2	59	−11.7	<0.001	0.89
1	Cup-cutter	Plant Height	14.0 ± 0.5	5.3 ± 0.2	59	−14.3	<0.001	0.94
2	Cup-cutter	Plant Height	16.3 ± 0.4	5.7 ± 0.3	59	−11.4	<0.001	0.93
1	Cup-cutter	Root Rating	1.3 ± 0.1	6.4 ± 0.2	59	−14.9	<0.001	0.94
2	Cup-cutter	Root Rating	1.0 ± 0.0	4.1 ± 0.3	59	−7.4	<0.001	0.76
2	Quadrat	Larval Density	0.8 ± 0.2	11.5 ± 1.6	59	−4.7	<0.001	0.63
3	Quadrat	Larval Density	3.6 ± 0.3	3.6 ± 0.1	43	−15.2	<0.001	0.97
2	Quadrat	Above-ground Biomass	29.0 ± 2.7	4.3 ± 0.2	59	−13.3	<0.001	0.93
3	Quadrat	Above-ground Biomass	51.7 ± 3.4	4.9 ± 0.1	43	−16.6	<0.001	0.97
2	Quadrat	Below-ground Biomass	26.3 ± 3.0	4.1 ± 0.2	59	−13.9	<0.001	0.92
3	Quadrat	Below-ground Biomass	84.1 ± 7.6	5.2 ± 0.2	43	−12.6	<0.001	0.94