Null Hypothesis: GDP has a unit root   
Exogenous: Constant, Linear Trend   
Lag Length: 5 (Automatic - based on SIC, maxlag=8)   
   
   t-Statistic   Prob.*
   
Augmented Dickey-Fuller test statistic   -6.007270  0.0002
Test critical values: 1% level  -4.309824
5% level  -3.574244
10% level  -3.221728
   
*MacKinnon (1996) one-sided p-values.   
   
   
Augmented Dickey-Fuller Test Equation   
Dependent Variable: D(GDP)   
Method: Least Squares   
Date: 08/20/15   Time: 10:22   
Sample (adjusted): 1986 2014   
Included observations: 29 after adjustments   
   
Variable Coefficient Std. Error t-Statistic Prob.  
   
GDP(-1) -1.367621 0.227661 -6.007270 0.0000
D(GDP(-1)) 0.860898 0.153723 5.600304 0.0000
D(GDP(-2)) 0.456267 0.150057 3.040630 0.0062
D(GDP(-3)) 0.716334 0.124592 5.749447 0.0000
D(GDP(-4)) 0.407396 0.124812 3.264061 0.0037
D(GDP(-5)) 0.333619 0.091694 3.638379 0.0015
C 10.79341 1.949832 5.535561 0.0000
@TREND("1980") 0.185038 0.045913 4.030167 0.0006
   
R-squared 0.795327     Mean dependent var  -0.224138
Adjusted R-squared 0.727103     S.D. dependent var  2.848390
S.E. of regression 1.487985     Akaike info criterion  3.861674
Sum squared resid 46.49610     Schwarz criterion  4.238859
Log likelihood -47.99427     Hannan-Quinn criter.  3.979804
F-statistic 11.65756     Durbin-Watson stat  2.051837
Prob(F-statistic) 0.000005   
   


Null Hypothesis: GDP has a unit root   
Exogenous: Constant   
Lag Length: 0 (Automatic - based on SIC, maxlag=8)   
   
   t-Statistic   Prob.*
   
Augmented Dickey-Fuller test statistic   -3.901305  0.0051
Test critical values: 1% level  -3.639407
5% level  -2.951125
10% level  -2.614300
   
*MacKinnon (1996) one-sided p-values.   
   
   
Augmented Dickey-Fuller Test Equation   
Dependent Variable: D(GDP)   
Method: Least Squares   
Date: 08/20/15   Time: 10:25   
Sample (adjusted): 1981 2014   
Included observations: 34 after adjustments   
   
Variable Coefficient Std. Error t-Statistic Prob.  
   
GDP(-1) -0.624064 0.159963 -3.901305 0.0005
C 6.776377 1.807732 3.748552 0.0007
   
R-squared 0.322324     Mean dependent var  0.097059
Adjusted R-squared 0.301146     S.D. dependent var  4.047332
S.E. of regression 3.383468     Akaike info criterion  5.332702
Sum squared resid 366.3313     Schwarz criterion  5.422488
Log likelihood -88.65593     Hannan-Quinn criter.  5.363321
F-statistic 15.22018     Durbin-Watson stat  2.016823
Prob(F-statistic) 0.000462   
   


请问该如何选择，只要有偏移项，有无趋势项都显著，到底应该选哪个？