Dear list members,

I am fitting a negative binomial model but I get a very large dispersion
parameter.  Why is that?

quine.nb2 <- glm.nb(Pt ~ Agua + Dist10, data = Abundancia)

summary(quine.nb2)

Deviance Residuals:
     Min        1Q    Median        3Q       Max
-2.20911  -0.67157   0.04411   0.35695   1.65524

Coefficients:
              Estimate Std. Error z value Pr(>|z|)
(Intercept)   -0.88354    0.43982  -2.009   0.0445 *
Agua[T.negra]  0.89319    0.43727   2.043   0.0411 *
Dist10         0.39416    0.04387   8.984   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

(Dispersion parameter for Negative Binomial(67552.88) family taken to be 1)

    Null deviance: 128.567  on 15  degrees of freedom
Residual deviance:  17.005  on 13  degrees of freedom
AIC: 67.058

Number of Fisher Scoring iterations: 1


              Theta:  67553
          Std. Err.:  1428117
Warning while fitting theta: iteration limit reached

 2 x log-likelihood:  -59.058


Best,

Manuel

-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspinola@una.ac.cr
mspinola10@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río <https://sites.google.com/site/lobitoderio/>
Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/>

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