[statnet_help] Changes in how standard errors are reported across ERGM versions

David Kretschmer dkretsch at mail.uni-mannheim.de
Mon Jul 27 00:39:15 PDT 2020


Dear all,

for a replication project, I have worked with an old version of the ERGM package (ergm-3.1.0) and the more recent versions (ergm-3.10.1, in particular) and I have a question on differences between these versions.

I have noticed that, for some of the networks I analyse, the ergm() command returns different results for the old and the new version. In particular, this holds true for networks in which some of the network parameters cannot be estimated from the data, as is obvious from the MCMC chain values having the same value across all iterations and the MCMC% in the ERGM output being NA (both in the old and the new version of ergm()).

However, the results between versions differ in the fact that, for those parameters that cannot be estimated, the newer ergm versions report the standard error as NA while the old ergm version reports a standard error that is basically indistinguishable from 0 (value of the order of 10^-15- 10^-30). In both versions, regular numeric values for the coefficients themselves are reported.

It seems clear to me that the ERGM estimates from these networks, or at least the estimates for these parameters, do not have a meaningful interpretation. Still, I am interested to learn 1) why, in the older versions of the ERGM package, these standard errors close to zero were reported and 2) when this behaviour changed.

Any help would be greatly appreciated.

Best,
David


--
David Kretschmer
University of Mannheim
Mannheim Centre for European Social Research (MZES)
A5, 6
68159 Mannheim, Germany
Tel.: +49-621-181-2024

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