我在EVIEWS上做高铁梅上的例题6.1,结果和她的结果略有出入,想问问是什么回事,
      1.Convergence achieved 她的是17我的是15.这个是不是指叠代次数啊
      2.Vaiance backcast 是什么意思啊?
Dependent Variable: LOG(SP)   
Method: ML - ARCH   
Date: 09/15/04   Time: 12:42   
Sample: 1/05/1998 12/31/2001   
Included observations: 1041   
Estimation settings: tol= 0.00010, derivs=accurate numeric (linear)   
Initial Values: C(1)=1.00003, C(2)=0.00015, C(3)=0.15000,   
        C(4)=0.60000   
Convergence achieved after 17 iterations   
Variance backcast: ON   
GARCH = C(2) + C(3)*RESID(-1)^2 + C(4)*GARCH(-1)   
   
Coefficient Std. Error z-Statistic Prob.  
   
LOG(SP(-1)) 1.000030 4.30E-05 23248.96 0.0000
   
Variance Equation   
   
C 1.19E-05 2.27E-06 5.266027 0.0000
RESID(-1)^2 0.251125 0.021861 11.48729 0.0000
GARCH(-1) 0.731307 0.021909 33.38002 0.0000
这是她的,下面的是我的
Dependent Variable: LOG(SP)   
Method: ML - ARCH (Marquardt) - Normal distribution   
Date: 05/23/07   Time: 10:09   
Sample: 1/05/1998 12/31/2001   
Included observations: 1041   
Convergence achieved after 15 iterations   
Variance backcast: ON   
GARCH = C(2) + C(3)*RESID(-1)^2 + C(4)*GARCH(-1)   
   
Coefficient Std. Error z-Statistic Prob.  
   
LOG(SP(-1)) 1.000030 4.30E-05 23249.14 0.0000
   
Variance Equation   
   
C 1.19E-05 2.27E-06 5.264760 0.0000
RESID(-1)^2 0.251086 0.021861 11.48533 0.0000
GARCH(-1) 0.731349 0.021909 33.38185 0.0000
请问我那里做的不对了呢?