Table 4.

Selected bowhead−killer whale interaction model (shown in Table 3) parameter estimates fitted using the clogit function and the TwoStepCLogit function for comparison

clogit functionTwoStepCLogit function
VariableCoefficientRobust SEzpCoefficientSE
SIconc−0.1190.243−0.4910.623−0.0050.364
Dkw0.3651.5450.2370.8121.8662.934
SI2conc−0.2010.084−2.3850.017−0.1710.079
Dsh−3.3620.508−6.610<0.0001−3.4460.988
SIconc:Dkw0.0140.0380.3850.700−0.0010.055
SI2conc:Dkw0.0230.0121.8980.0570.0190.011
Dkw:Dsh0.4230.0686.174<0.00010.4450.138
Dedge:isice = 01.2230.9121.3400.1801.0550.636
Dedge:isice = 12.3490.5744.089<0.00011.8800.916
Dkw:Dedge:isice = 0−0.1500.128−1.1690.242−0.1270.089
Dkw:Dedge isice = 1−0.321−0.073−4.393<0.0001−0.2540.121
  • Parameter estimates, parameter SEs, and levels of significance are comparable for both fitting methods. See Table 1 for definition of terms. z, = z-score on a standard normal distribution. Bolded p values are statistically significant.