Table 5.

Ordered probit regression results—linear model (a) and interactions model (b)

Variables	Linear (a)		Interactions (b)
	Coefficient	z-statistic	Coefficient	z-statistic
Linear variables
PG6001	0.035	0.50
Min Temp2	−0.011	−1.77
Synchronization Device Reuse	−0.27***	−7.66	−0.27***	−7.42
CIDR3	−0.13	−1.94
Day of the year	−0.0017	−1.60	0.045***	3.10
Non-linear variable
Day of the year (second order)4			−0.00011***	−3.23
Dose interactions
PG600 x CIDR			189***	2.99
PG600 x SMB5			179***	2.96
PG600 (second order) x CIDR			−129***	−3.00
PG600 (second order) x SMB			−123***	−3.05
PG600 (third order) x CIDR			43***	3.01
PG600 (third order) x SMB			40***	3.01
PG600 (fourth order) x CIDR			−7.0***	−3.02
PG600 (fourth order) x SMB			−6.3***	−2.92
PG600 (fifth order) x CIDR			0.44***	3.01
PG600 (fifth order) x SMB			0.38***	2.79
Temperature interactions
Min Temp x PG600 x CIDR			−0.028	−1.01
Min Temp x PG600 x SMB			0.18***	3.15
Min Temp (second order) x PG600 x CIDR			0.00017	0.67
Min Temp (second order) x PG600 x SMB			−0.0018***	−3.23

***Significant at the 99% confidence level.

¹PG600 (Merck Animal Health, Summit, NJ).

²Min Temp = Minimum Daily Temperature, °C.

³CIDR = controlled internal drug releasing device (Pfizer Inc., New York, NY).

⁴Second-order variables are squared (y²), third order are cubic (y³), and so on.

⁵SMB = Syncro-Mate-B device (Sanofi Animal Health, Overland Park, KS).