Table 6.

Models using Harris et al. (2001) determinants relating urinary 2,4-D concentration to work practice and task data from County Noxious Weed Applicators in Kansas under weighting schemes C, D, and E.

Variable	Beta	90% CI	P-value	AIC	Between-worker variancea	Within-worker variancea	Semipartial R2
Model C
Ln-creatinine concentration (ln-g/l)	1.5	1.1, 1.8	<0.0001	445.3	1.9	1.0	22.7%
Spraying from backpack (weighted yes/no)	2.4	−0.6, 5.5	0.002b				0.6%
Spraying from hand-held (weighted yes/no)	1.9	0.7, 3.2	—				2.9%
Spraying from open cab truck (weighted yes/no)	−0.4	−1.8, 1.1	—				0%
Spraying from closed cab truck (weighted yes/no)	−0.3	−1.6, 1.1	—				0%
Month
April	−1.7	−3.0, −0.3	0.02c				4.9%
May	−1.6	−2.8, −0.4	—				—
June	−0.8	−1.9, 0.2	—				—
July	−0.7	−1.8, 0.4	—				—
August	—	—	—				—
Application concentration (qt/acre)	1.3	0.4, 2.1	0.02				1.8%
Wet gloves (weighted yes/no)	0.9	−0.3, 2.1	0.2				0.4%
Ln-total time all activities (weighted ln-minutes)	0.5	0.04, 0.9	0.07				1.3%
Model D
Ln-creatinine concentration (ln-g/l)	1.5	1.2, 1.8	<0.0001	444.5	2.1	1.0	24.8%
Spraying from backpack (weighted yes/no)	3.8	0.8, 6.9	0.002b				2.0%
Spraying from hand-held (weighted yes/no)	1.3	−0.04, 2.6	—				1.1%
Spraying from open cab truck (weighted yes/no)	−0.4	−1.8, 1.0	—				0.1%
Spraying from closed cab truck (weighted yes/no)	−0.8	−2.1, 0.6	—				0.5%
Month
April	−2.0	−3.3, −0.6	0.006c				6.3%
May	−1.9	−3.0, −0.8	—				—
June	−1.2	−2.3, −0.1	—				—
July	−1.0	−2.0, 0.1	—				—
August	—	—	—				—
Application concentration (qt/acre)	1.3	0.4, 2.2	0.02				1.2%
Wet gloves (weighted yes/no)	1.6	0.3, 2.9	0.05				1.4%
Ln-total time all activities (weighted ln-minutes)	0.1	0.01, 0.3	0.08				1.4%
Model E
Ln-creatinine concentration (ln-g/l)	1.5	1.2, 1.8	<0.0001	441.2	1.9	1.0	24.3%
Spraying from backpack (weighted yes/no)	2.8	0.1, 5.6	0.002b				1.3%
Spraying from hand-held (weighted yes/no)	1.5	0.2, 2.8	—				1.7%
Spraying from open cab truck (weighted yes/no)	−0.6	−2.0, 0.8	—				0.1%
Spraying from closed cab truck (weighted yes/no)	−0.8	−2.0, 0.5	—				0.4%
Month
April	−1.8	−3.1, −0.4	0.01c				5.1%
May	−1.8	−2.9, −0.7	—				—
June	−1.0	−2.1, 0.07	—				—
July	−0.8	−1.9, 0.2	—				—
August	—	—	—				—
Application concentration (qt/acre)	1.3	0.4, 2.2	0.02				1.8%
Wet gloves (weighted yes/no)	1.2	−0.03, 2.4	0.1				0.8%
Ln-total time all activities (weighted ln-minutes)	0.6	0.2, 1.0	0.01				2.5%

^aIn model with ln-creatinine and random subject effects, ${\sigma }_{\text{b}}^2=2.5$ and ${\sigma }_{\text{w}}^2=1.3$.

^bFour-spray method variables assessed as single group in models with four degrees of freedom likelihood ratio test.

^cF-test for group effect of month variables.