Archive for March 11, 2013

Oh what a tangled web we weave…

Posted in Bad Statistics with tags , , , , , , on March 11, 2013 by telescoper

..when first we practice frequentist statistics!

I couldn’t resist a quick post directing you to a short paper on the arXiv with the following abstract:

I use archival data to measure the mass of the central black hole in NGC 4526, M = (4.70 +- 0.14) X 10^8 Msun. This 3% error bar is the most precise for an extra-galactic black hole and is close to the precision obtained for Sgr A* in the Milky Way. The factor 7 improvement over the previous measurement is entirely due to correction of a mathematical error, an error that I suggest may be common among astronomers.

The “mathematical error” quoted in the abstract involves using chi-squared-per-degree-of-freedom instead of chi-squared instead of the full likelihood function instead of the proper, Bayesian, posterior probability. The best way to avoid such confusion is to do things properly in the first place. That way you can also fold in errors on the distance to the black hole, etc etc…


Always seeking greater silence

Posted in Poetry with tags , , , on March 11, 2013 by telescoper

Just a quick plug for a fascinating programme I heard on BBC Radio 3 last night about the great Welsh poet R.S. Thomas. It’s called Always Seeking Greater Silence and it is available on iPlayer for your listening pleasure.

Here’s an excerpt from the published description of the programme:

RS Thomas was a man full of contradictions, but one constant was his passion for birdwatching. Towards the end of his life he said that ‘the deity has chosen to reveal himself to me via the world of nature’. He also declared that he preferred to be alone with nature than be with human beings. Bird imagery in particular provided him with a means of symbolising renewal, nourishment and femininity in his poetry, but also of exploring his faith in God. Increasingly towards the end of his life, his bird poems explored the space between faith and doubt. In ‘Sea-watching,’ he directly associates bird-watching with prayer: ‘Ah, but a rare bird is/ rare. It is when one is not looking/ at times one is not there/ that it comes’.

I have the utmost admiration for R.S. Thomas as a poet, but I do wonder how effective he was as a priest looking after his flock when he could come out with statements like the following:

I’ve had more pleasure from being alone with the natural creation than I have with human beings. Human beings are responsible for so much unhappiness and cruelty and failure that one is not terribly enthusiastic about them.

This rather bleak view of humanity explains to some extent why so many of his poems are about the natural world rather than people, but he is unlike many other “nature poets” in that his voice is unflinching and devoid of sentimentality. Although not religious myself, I also deeply respect his openness about his struggle with faith and doubt – he seems to me to have been a man who was deeply allergic to superficiality, a trait which also manifests itself in his verse.

It is the centenary of the birth of R.S. Thomas on 29th March 2013. I hope I remember to mark the occasion with an appropriate poem.