Table 3 Negative Binomial Regressions for Number of Person-Trips: All Purposes and Recreational Purposes

Table 3
Negative Binomial Regressions for Number of Person-Trips: All Purposes and Recreational Purposes

  Variable Beta SE t-stat P-value Negative binomial regression Poisson regression
Dependent variable: number of person-trips for all purposes Constant 1.672 0.012 138.00 0.000    
HH members per vehicle owned 0.255 0.004 59.20 0.000    
Income per household member -3.16E-06 2.77E-07 -11.40 0.000    
Population density -4.42E-06 6.10E-07 -7.25 0.000    
Vehicle age -0.014 0.001 -20.80 0.000    
Weekend day indicator 0.100 0.007 13.50 0.000    
SUV indicator 0.045 0.012 3.85 0.000    
Pickup indicator -0.164 0.011 -14.90 0.000    
Minivan indicator 0.302 0.011 28.50 0.000    
Over-dispersion parameter 0.351 0.004 97.10 0.000    
Log-likelihood Function for number of person-trips for all purposes Constant only         -121,113.3 -160,951.3
Convergence         -117,983.1 -148,642.7
Pseudo-R2         0.026 0.076
Dependent variable: number of person-trips for recreational purposes Constant 0.485 0.021 22.80 0.000    
HH members per vehicle owned 0.204 0.008 25.90 0.000    
Income per household member -3.14E-06 4.73E-07 -6.60 0.000    
Population density -6.12E-06 1.09E-06 -5.60 0.000    
Vehicle age -0.018 0.001 -15.60 0.000    
Weekend day indicator 0.590 0.014 41.40 0.000    
SUV indicator 0.005 0.021 0.20 0.814    
Pickup indicator -0.292 0.019 -15.20 0.000    
Minivan indicator 0.308 0.020 15.70 0.000    
Over-dispersion parameter 1.009 0.011 93.40 0.000    
Log-likelihood function for number of person-trips for recreational purposes Constant only         -82,460.37 -10,6536.4
Convergence         -80,612.10 -99,753.51
Pseudo-R2         0.022 0.064

Number of observations: 41,538 vehicles
Model form: Number of person-trips ~ negative binomial with expected value exp(β′X) and non-negative over-dispersion parameter