[R] doubt about DF in survival model

[Ronaldo Reis Jr.]

Hi all,

I have this,

Weibull distribution
n= 1000

> anova(pk.m0)
     Df Deviance Resid. Df   -2*LL P(>|Chi|)
NULL NA       NA       999 1451.31        NA

> anova(pk.m0,pk.m1)
      Terms Resid. Df    -2*LL    Test Df   Deviance    P(>|Chi|)
1         1       998 1451.310         NA         NA           NA
2      seed       996 1229.714          2  221.59557 7.605594e-49

With   n=1000,
Df of  Null Model (pk.m0) = 999, it is ok, to me.

But, when I put together Null Model (pk.m0) and the Seed Model (pk.m1),
Df of the Null model changed to 998.

My question is, why it does happen?

Thanks
inte
Ronaldo
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