31.5 Bayesian bootstrap and bagging

A Bayesian estimator may be analyzed with the bootstrap in exactly the same way as a (penalized) maximum likelihood estimate. For example, the posterior mean and posterior median are two different Bayesian estimators. The bootstrap may be used estimate standard errors and confidence intervals, just as for any other estimator.

(Huggins and Miller 2019) use the bootstrap to assess model calibration and fitting in a Bayesian framework and further suggest using bagged estimators as a guard against model misspecification. Bagged posteriors will typically have wider posterior intervals than those fit with just the original data, showing that the method is not a pure Bayesian approach to updating, and indicating it would not be calibrated if the model were well specified. The hope is that it can guard against over-certainty in a poorly specified model.

References

Huggins, Jonathan H, and Jeffrey W Miller. 2019. “Using Bagged Posteriors for Robust Inference and Model Criticism.” arXiv, no. 1912.07104.