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From |
brendan.halpin@ul.ie (Brendan Halpin) |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: RE: Re: Loglinear quasi-symmetric agreement |

Date |
Mon, 11 Jun 2012 21:20:17 +0100 |

On Fri, Jun 08 2012, Scholes, Shaun wrote: > The problem may be due to the presence of zero counts in the dataset rather than using -xi-/not using -xi-. That is right. -glm- is trying to estimate the log of 0 and/or infinity and failing. Instead it is giving you a big number with a huge SE. However, there is more to the xi/not xi difference than meets the eye. I suspect the count variable has been changed (e.g., by replacing zero cells with a small number such as 0.001 or adding such a constant to all cells, a practice less in favour than it used to be, but recommended by Agresti). Computers find it much easier to deal with log(0.001). . gen n = count . replace n = 0.001 if count==0 . glm n i.px i.py i.qasym, fam(poi) Generalized linear models No. of obs = 16 Optimization : ML Residual df = 3 Scale parameter = 1 Deviance = .9782177411 (1/df) Deviance = .3260726 Pearson = 1.580424814 (1/df) Pearson = .5268083 Variance function: V(u) = u [Poisson] Link function : g(u) = ln(u) [Log] AIC = 4.237908 Log likelihood = -20.90326338 BIC = -7.339548 ------------------------------------------------------------------------------ | OIM n | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- px | 2 | -6.954584 28.884 -0.24 0.810 -63.56618 49.65701 3 | -6.294418 28.87475 -0.22 0.827 -62.88789 50.29905 4 | 4.536497 28.87152 0.16 0.875 -52.05064 61.12364 | py | 2 | -7.627542 28.88293 -0.26 0.792 -64.23705 48.98197 3 | -4.794332 28.87187 -0.17 0.868 -61.38215 51.79349 4 | -5.324955 28.87152 -0.18 0.854 -61.91209 51.26218 | qasym | 2 | 5.397211 28.88398 0.19 0.852 -51.21434 62.00876 3 | 2.195089 28.8786 0.08 0.939 -54.40594 58.79611 4 | -16.14475 76.37546 -0.21 0.833 -165.8379 133.5484 5 | 13.43699 57.763 0.23 0.816 -99.77641 126.6504 6 | 11.32266 57.74145 0.20 0.845 -101.8485 124.4938 7 | 0 (omitted) 8 | 11.58123 57.73826 0.20 0.841 -101.5837 124.7461 9 | 0 (omitted) 10 | 0 (omitted) | _cons | 3.091042 .2132007 14.50 0.000 2.673177 3.508908 ------------------------------------------------------------------------------ Regards, Brendan -- Brendan Halpin, Department of Sociology, University of Limerick, Ireland Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F1-009 x 3147 mailto:brendan.halpin@ul.ie ULSociology on Facebook: http://on.fb.me/fjIK9t http://teaching.sociology.ul.ie/bhalpin/wordpress twitter:@ULSociology * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Re: Loglinear quasi-symmetric agreement***From:*Martyn Sherriff <statams48@gmail.com>

**st: RE: Re: Loglinear quasi-symmetric agreement***From:*"Scholes, Shaun" <s.scholes@ucl.ac.uk>

**st: RE: RE: Re: Loglinear quasi-symmetric agreement***From:*"Scholes, Shaun" <s.scholes@ucl.ac.uk>

**Re: st: RE: RE: Re: Loglinear quasi-symmetric agreement***From:*Martyn Sherriff <statams48@gmail.com>

**Re: st: RE: RE: Re: Loglinear quasi-symmetric agreement***From:*Martyn Sherriff <statams48@gmail.com>

**RE: st: RE: RE: Re: Loglinear quasi-symmetric agreement***From:*"Scholes, Shaun" <s.scholes@ucl.ac.uk>

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