Oct 15th, 2009| 06:46 pm | Posted by hlee

Astronomers rely on scatter plots to illustrate correlations and trends among many pairs of variables more than any scientists^{[1]}. Pages of scatter plots with regression lines are often found from which the slope of regression line and errors bars are indicators of degrees of correlation. Sometimes, too many of such scatter plots makes me think that, overall, resources for drawing nice scatter plots and papers where those plots are printed are wasted. Why not just compute correlation coefficients and its error and publicize the processed data for computing correlations, not the full data, so that others can verify the computation results for the sake of validation? A couple of scatter plots are fine but when I see dozens of them, I lost my focus. This is another cultural difference. Continue reading ‘Scatter plots and ANCOVA’ »

Tags:

ANCOVA,

ANOVA,

approximation,

correlation,

Gaussianity,

graphics,

MADS,

modeling,

nonparametric,

parallel coordinates,

PCA,

quality,

quantity,

regression,

scatter plots Category:

arXiv,

Cross-Cultural,

Fitting,

Jargon,

Methods,

Stat,

Uncertainty |

Comment
Mar 6th, 2009| 09:22 am | Posted by vlk

What XKCD says:

The mouseover text on the original says *“Correlation doesn’t imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing ‘look over there’.”*

It is a bad habit, hard to break, the temptation is great.

May 28th, 2008| 01:00 pm | Posted by vlk

The most widely used tool for detecting sources in X-ray images, especially Chandra data, is the wavelet-based `wavdetect`, which uses the Mexican Hat (MH) wavelet. Now, the MH is not a very popular choice among wavelet aficianados because it does not form an orthonormal basis set (i.e., scale information is not well separated), and does not have compact support (i.e., the function extends to inifinity). So why is it used here?

Continue reading ‘Mexican Hat [EotW]’ »

Tags:

Chandra,

ciao,

convolution,

correlation,

EotW,

Equation,

Equation of the Week,

Fourier Transform,

gaussian,

MexHat,

Mexican Hat,

MH,

multiscale,

wavdetect,

wavelet Category:

Algorithms,

Astro,

Imaging,

Jargon |

1 Comment
Jan 25th, 2008| 12:53 pm | Posted by hlee

I have been observing some sorts of misconception about statistics and statistical nomenclature evolution in astronomy, which I believe, are attributed to the lack of references in the astronomical society. There are some textbooks designed for junior/senior science and engineering students, which are likely unknown to astronomers. Example-wise, these books are not suitable, to my knowledge. Although I never expect astronomers to learn standard graduate (mathematical) statistics textbooks, I do wish astronomers go beyond Numerical Recipes (W. H. Press, S. A. Teukolsky, W. T. Vetterling, & B. P. Flannery) and Error Data Reduction and Analysis for the Physical Sciences (P. R. Bevington & D. K. Robinson). Here are some good ones written by astronomers, engineers, and statisticians: Continue reading ‘Books – a boring title’ »

Tags:

application,

Bayesian,

book,

books,

box plot,

cartoon,

chi-square,

CLT,

correlation,

delta method,

EDA,

error bars,

Frequentist,

gaussian,

references,

scatter plot Category:

Cross-Cultural,

Data Processing,

Misc,

Stat |

12 Comments
Jan 18th, 2008| 02:24 pm | Posted by hlee

Seven preprints were chosen this week and two mentioned model selection. Continue reading ‘[ArXiv] 3rd week, Jan. 2008’ »

Tags:

AIC,

Bayesian,

BIC,

CLT,

correlation,

F-test,

FoF,

hypothesis testing,

Kolmogorov-Smirnoff test,

LRT,

Model Selection,

modeling,

sunspots Category:

arXiv |

Comment
Jan 11th, 2008| 03:44 pm | Posted by hlee

It is notable that there’s an astronomy paper contains **AIC, BIC**, and **Bayesian evidence** in the title. The topic of the paper, unexceptionally, is cosmology like other astronomy papers discussed these (statistical) information criteria (I only found a couple of papers on model selection applied to astronomical data analysis without articulating CMB stuffs. Note that I exclude Bayes factor for the model selection purpose).

To find the paper or other interesting ones, click Continue reading ‘[ArXiv] 2nd week, Jan. 2007’ »

Tags:

AIC,

Bayesian evidence,

BIC,

catalog,

Classification,

CMB,

confidence interval,

consistency,

correlation,

GRB,

information criterion,

Model Selection,

SDSS,

test,

WMAP Category:

arXiv |

Comment
Dec 21st, 2007| 01:47 pm | Posted by hlee

It’s a report about the job market in US.

[astro-ph:0712.2820] ** The Production Rate and Employment of Ph.D. Astronomers ** T.S. Metcalfe

Continue reading ‘[ArXiv] Astronomy Job Market in US’ »

Jun 18th, 2007| 05:08 pm | Posted by hlee

One of arxiv/astro-ph preprints, arxiv/0706.1703v1 discusses **correlation** between galactic HI and the cosmic microwave background (CMB) and reports no statistically significant correlation.

Continue reading ‘[ArXiv] Correlation Studies, June 12, 2007’ »