Users should verify that the Markov Chain converges to its stationary
distribution. After running the zelig() function but before
performing setx(), users may conduct the following
convergence diagnostics tests:
- geweke.diag(z.out$coefficients): The Geweke diagnostic tests
the null hypothesis that the Markov chain is in the stationary distribution
and produces z-statistics for each estimated parameter.
- heidel.diag(z.out$coefficients): The Heidelberger-Welch
diagnostic first tests the null hypothesis that the Markov Chain is in the
stationary distribution and produces p-values for each estimated parameter.
Calling heidel.diag() also produces
output that indicates whether the mean of a marginal posterior distribution
can be estimated with sufficient precision, assuming that the Markov Chain is
in the stationary distribution.
- raftery.diag(z.out$coefficients): The Raftery diagnostic
indicates how long the Markov Chain should run before considering draws from
the marginal posterior distributions sufficiently representative of the
stationary distribution.
If there is evidence of non-convergence, adjust the values
for burnin and mcmc and rerun zelig().
Advanced users may wish to refer to help(geweke.diag),
help(heidel.diag), and help(raftery.diag) for more
information about these diagnostics.
Gary King
2007-06-01