Table 3.

Coefficients of linear regression analysis, log mg/PCU as dependent variable, percentage of PCU related to pigs and poultry as well as animal density (cubic transformation) as independent variables

	Regression coefficients b	t statistic	p value	95% Confidence interval
				Lower limit	Upper limit
Constant	1.784	29.129	<.0001	1.658	1.910
Percentage of PCU related to pigs and poultrya	0.020	4.675	<.001	0.011	0.028
Animal density in PCU/km2 a	0.076	3.455	.002	0.031	0.121
(Animal density in PCU/km2)2 a	−0.002	−3.243	.003	−0.004	−0.001
(Animal density in PCU/km2)3 a	0.00002	2.787	.010	0.000	0.000

^aVariables were centred. Constant corresponds to 41.4% pigs and poultry at 15.97 PCU/km², 577.22 (PCU/km²)² and 31,937 (PCU/km²)³.