May 30th, 2007| 11:11 am | Posted by hlee

John Rice is visiting IIC. The meeting and his talk is scheduled on Friday, June 8, at 11:30am (room 403 at 60 Oxford St.).

Title: Event Weighted Tests for Periodicity in a Sequence of Photon Arrival Times:

Detecting Gamma-ray Pulsars.

**[Added]** Another meeting is scheduled at the stat dept. located in Science Center, 4-6pm, Wednesday (June 6th).

May 29th, 2007| 06:12 pm | Posted by aconnors

Marty Weinberg , January 26, 2006, at the opening day of the Source and Feature Detection Working Group of the SAMSI 2006 Special Semester on Astrostatistics :

You can’t think about source detection and feature detection

without thinking of what you are going to use them for. The

ultimate inference problem and source/feature detection need to

go together.

May 25th, 2007| 04:30 pm | Posted by vlk

Despite some recent significant advances in Statistics and its applications to Astronomy (Cash 1976, Cash 1979, Gehrels 1984, Schmitt 1985, Isobe et al. 1986, van Dyk et al. 2001, Protassov et al. 2002, etc.), there still exist numerous problems and limitations in the standard statistical methodologies that are routinely applied to astrophysical data. For instance, the basic algorithms used in non-linear curve-fitting in spectra and images have remained unchanged since the 1960′s: the downhill simplex method of Nelder & Mead (1965) modified by Powell, and methods of steepest descent exemplified by Levenberg-Marquardt (Marquardt 1963). All non-linear curve-fitting programs currently in general use (Sherpa, XSPEC, MPFIT, PINTofALE, etc.) with the exception of Monte Carlo and MCMC methods are implementations based on these algorithms and thus share their limitations.

Continue reading ‘On the unreliability of fitting’ »

Tags:

best-fit,

chi-square,

chisq,

Fitting,

levenberg-marquardt,

MCMC,

steepest descent Category:

Bad AstroStat,

Data Processing,

Fitting,

Frequentist,

Methods,

Spectral,

Stat,

Uncertainty |

2 Comments
May 25th, 2007| 11:51 am | Posted by vlk

It seems to be necessary to devise a good system of categories beforehand with wordpress, because plain tags are not (yet?) implemented. Categories can only be defined by the admin, so it is useful to have as comprehensive a list as possible. I suggest the following set:

Continue reading ‘Categories’ »

May 22nd, 2007| 06:45 pm | Posted by aconnors

Xiao Li Meng, on the Banff Challenge, speaking at the First GLAST Symposium , 8 Feb 2007, AstroStat Special Session :

“Aneta [Siemiginowska] has asked me to explain the difference between frequentist and Bayesian methods. That is quite easy!”

(pause)

“One is right, and the other is wrong.”

( pause)

“The only trouble is, which is which?”