Jun 2nd, 2009| 03:03 am | Posted by hlee

Even though I traced the astronomers’ casual usage of the **null hypothesis probability** in a fashion of reporting outputs from data analysis packages of their choice, there were still some curious cases of the **null hypothesis probability** that I couldn’t solve. They are quite mysterious to me. Sometimes too much creativity harms the original intention. Here are some examples. Continue reading ‘Curious Cases of the Null Hypothesis Probability’ »

Tags:

cases,

chi-sq,

curious,

degree of freedom,

dof,

F-test,

goodness-of-fit test,

Model Selection,

null hypothesis probability,

p-value,

reduced chi-sq Category:

arXiv,

Astro,

Cross-Cultural,

Fitting,

Methods,

Uncertainty |

3 Comments
Jul 16th, 2008| 01:00 pm | Posted by vlk

The Χ^{2} distribution plays an incredibly important role in astronomical data analysis, but it is pretty much a black box to most astronomers. How many people know, for instance, that its form is exactly the same as the γ distribution? A Χ^{2} distribution with ν degrees of freedom is

**p(z|ν) = (1/Γ(ν/2)) (1/2)**^{ν/2} z^{ν/2-1} e^{-z/2} ≡ γ(z;ν/2,1/2) , where **z=Χ**^{2}.

Continue reading ‘chi-square distribution [Eqn]’ »

Mar 21st, 2008| 06:20 pm | Posted by hlee

Markov chain Monte Carlo (MCMC) never misses a week from recently astro-ph. A book titled *MCMC in astronomy* will be a best seller. There are, in addition, very interesting non MCMC preprints. Continue reading ‘[ArXiv] 3rd week, Mar. 2007’ »

Tags:

chi-sq,

Fourier Analysis,

GREAT08,

lensing,

likelihood,

misnomer,

Poisson noisy image,

sparse Category:

arXiv,

Cross-Cultural,

Jargon,

MCMC |

Comment