In Output 4.2, all rhat values are below 1.01, but ess_bulk for sigma is about 600, much lower than for the coefficients. What is the best conclusion?

Question

Answer

The posterior for sigma is wider than the other posteriors, because ess_bulk measures posterior spread.

Answer

The prior for sigma dominates the data, because its effective sample size is smaller.

Answer

The chains have converged, but sigma's draws are more autocorrelated, so it is less precise.

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The rhat for sigma is the largest, so sigma is the only parameter that cannot be estimated.

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The sampler failed for sigma, because any ess_bulk below the number of draws means non-convergence.

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In Output 4.2, all rhat values are below 1.01, but ess_bulk for sigma is about 6...

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