objective Bayes; really old data

Today was day two with the Galactic Center Group at UCLA. Again, a huge argument about priors broke out. As my loyal reader knows, I am a subjective Bayesian, not an objective Bayesian. Or more correctly “I don't always adopt Bayes, but when I do, I adopt subjective Bayes!” But the argument was about the best way to set objective-Bayes priors. My position is that you can't set them in the space of your parameters, because your parameterization itself is subjective. So you have to set them in the space of your data. That's exactly what the Galactic Center Group at UCLA is doing, and they can show that it gives them much better results (in terms of bias and coverage) than setting the priors in dumber “flat” ways (which is standard in the relevant literature).

One incredible thing about the work of this group is that they are still using, and still re-reducing, imaging data taken in the 1990s! That means that they are an amazing example of curation and preservation of data and reproducibility and workflow and etc. For this reason, there were information scientists at the meeting this week. It is an interesting consideration when thinking about how a telescope facility is going to be used: Will your data still be interesting 22 years from now? In the case of the Galactic Center, the answer turns out to be a resounding yes.

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