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Surveys and Population Studies

A Working Group in the Astrostatistics Program

Group Leaders: Tom Loredo (leader), Jogesh Babu (alternate), and Hyunsook Lee (web)

Meeting Time: Wednesdays 3:30 - 5:00 pm (unless otherwise noted)
Location: NISS building, 2nd floor classroom (203)
This week's agenda and readings

 

Remote access for the meetings is available:
Via teleconference at 919-685-9338 (not earlier than 9:40 am)
Via webcam — See instructions (pdf)

 

Note: Until we can get the needed bandwidth, equipment, etc. for broadcasting meetings via a webcam, SAMSI will be employing the following process for remote participation in working groups. A webcam picture will be available for viewing during the meetings. However, for audio, participants will have to call into the conference line.

Contents

Overview and Topics

Astronomers survey events and sources across the full range of astronomical disciplines, from the study of flaring events on the Sun and the distribution of minor planets in the solar system, to the study of the distributions of stars and compact objects in the Galaxy, and extending to the distribution of galaxies and explosive transient sources throughout the visible cosmos. The catalogs produced by such surveys span a factor of tens of millions in size, leading to a great diversity in the range of scientific questions and methodological issues data analysts must address.

Despite the great diversity in the subjects and sizes of astronomical surveys, there are common themes that arise throughout survey data analysis work. The most fundamental is the inherently hierarchical nature of survey data analysis. The scientific questions driving a survey project typically concern inferring properties of a population of sources; yet to address such questions, one must also carefully address statistical issues on the individual source level, such as source detection and measurement uncertainty, or source classification. Source- and population-level inferences often "feed back" to each other, with source uncertainties influencing population inferences, yet population properties influencing quantification of source characteristics. The classic example is Malmquist bias, where correct inference of population averages requires adjustment of individual source properties, but the size of the adjustment depends on the shape of the (unknown!) source distribution.

The SPS working group will explore a wide variety of topics at the interface of survey and sampling analysis in statistics, and the analysis of surveys of various types and sizes in astronomy. Following is a list of initial topics arising in discussions at the SAMSI Astrostatistics Workshop. We plan to identify a few of these for focused study, particularly during our focused research session from 20-31 March 2006.

Source Uncertainties

Source characteristics are often uncertain due to measurement error (e.g. for flux or magnitude distributions), or due to propagated uncertainty when they are inferred from other measured quantities (e.g., luminosities estimated from luminosity indicators, redshifts estimated from photometry). The uncertainties significantly complicate inference about the population. Source uncertainties grow as candidate sources become dim and harder to detect; source uncertainty is thus intimately related to the truncation or selection of the sample. We will study both quantification of source uncertainties and truncation/selection effects, and propagation of uncertainty through population-level inferences.

Methodology vs. Sample Size

Astronomical survey data sets have sample sizes ranging from dozens to hundreds of millions. Large data sets offer the promise of detailed inferences, but sound inferences may require computations that are challenging for huge samples. We will examine various tradeoffs one must make between methodological complexity and sample size.

Model Selection

Astronomer members of the SPS team are very interested in improving astrostatistical practice for comparing parametric models, including accounting for uncertainty in model selection. This is interesting both for the analysis of particular candidate sources found in a survey (i.e., for source detection and classification within a survey catalog), and for comparison of models for populations.

Agendas for Meetings

Date Topics & Readings Attendees

Wed., 8 Feb

First SPS working group meeting: Read the group overview (above) and the Feigelson & Babu (1998) and Petrosian (2002) reviews. We will discuss topics and readings for upcoming meetings. Please consider preparing a presentation (e.g., shared via a PDF file posted here) for an upcoming meeting.


References for Survival Analysis
Summary of the meeting

Remote: David Chernoff, Martin Hendry, Kuo-Ping Li, and Martin Weinberg
At SAMSI: Jogesh Babu, Pablo de la Cruz, Woncheol Jang, Hyunsook Lee, Ji Meng Loh, Tom Loredo, and Francisco Vera

Wed., 15 Feb

Second meeting: Tom's presentation
Astronomical Size-Frequency Distributions: The Role of Measurement Error


References for saddlepoint approximations and Neyman-Scott problem

Remote:Ruth Barrera, David Chernoff, Kuo-Ping Li, Tom Loredo, and Martin Weinberg
At SAMSI: Jogesh Babu, Matthew Fleenor, Woncheol Jang, Hyunsook Lee, and Ji Meng Loh

Wed., 22 Feb

Two presentations were given:

A few reading suggestions and a website about trigonometric parallex for statisticians

Martin's talk will be continued next week.

Remote: David Chernoff, Martin Hendry, Tom Loredo, Haywood Smith, Martin Weinberg, and unreconized members
At SAMSI: Matthew Fleenor, Woncheol Jang, Bill Jefferys, Hyunsook Lee, Ji Meng Loh, and UT students (Steven and Nathan)

Wed., 1 March

Martin Hendry:"What do astronomers mean by Malmquist bias?"


We are experiencing lots of noises during telecon (other groups have far less). Please, consider the followings:
  • Instead of speakers, use headphones or earphones if you are using internet phonecall services (This helps avoiding echos)
  • Use narrow beam or good sampling microphones (Some microphones catch all directional sounds regardless of distances. This helps avoiding background noises)
  • Be conscious when you are switching to speaker phones from regular phones.
Tom's email regarding noise reduction

Remote: Ruth Barrera, David Chernoff, Alanna Connors, Martin Hendry, Woncheol Jang, Tom Loredo, Haywood Smith, Antonio Uribe, Martin Weinberg, Steven (from UT) and unreconized members
At SAMSI: Jogesh Babu, Bill Jefferys, and Hyunsook Lee

Wed., 8 March

Jogesh Babu and Woncheol Jang:
"Selection Biases: Truncation and Censoring"

Check Particle Physics group website for some presentation materials.


Recommended papers
Possible collaborations among statisticians in point process, spatial statistics and astronomers with survey data?

Remote: Ruth Barrera, David Chernoff, Tom Loredo, Haywood Smith, Antonio Uribe
At SAMSI: Jogesh Babu, Matt Fleenor, Ji Meng Loh, Bill Jefferys, and Hyunsook Lee

Wed., 15 March

Tom Loredo:"Coincidence Assessment" and references (also listed in Tom's email)

Remote: Ruth Barrera, David Chernoff, Alanna Connors, Martin Hendry, and Antonio Uribe
At SAMSI:Woncheol Jang, Tom Loredo, Ji Meng Loh, Hyunsook Lee and Michael Woodroofe

Mon., 20 March

Open Colloquium (10:00-11:30am at SAMSI, Rm. 203)
Michael Woodroofe:"Shape Restricted Estimation with Applications to Astronomy"
.

Wed., 22 March

Martin Hendry:"The Best of Both Worlds?" [in PDF] (PPT file is small in size)


Jogesh Babu:"Multivariate K-S and other related statistics" (Lecture note from Mar. 6th Astrostat seminar, check from pg 13.)

Remote: Ruth Barrera, Haywood Smith, Antonio Uribe, and Martin Weinberg
At SAMSI:Jogesh Babu, Brendon Brewer, David Chernoff, Pablo de la Cruz, Matthew Fleenor, Martin Hendry, Woncheol Jang, Tom Loredo, Ji Meng Loh, Hyunsook Lee, David van Dyke, Michael Woodroofe, and Zhengyuan Zhang

Tue., 28 March

We will meet at 1:30pm. (Note the date change.)
Pablo de la Cruz and Vicent Martinez: "Some statistics for the large scale structure"


Quite number of references were discussed

Remote: Vincent Martinez, Haywood Smith, and Antonio Uribe
At SAMSI:Jogesh Babu, Brendon Brewer, David Chernoff, Pablo de la Cruz, Matthew Fleenor, Martin Hendry, Bill Jefferys, Woncheol Jang, Tom Loredo, Ji Meng Loh, Hyunsook Lee, Ramani Pilla, and Michael Woodroofe

Wed., 5 April

Tom Loredo: "Recap on recent meetings"
References mentioned

Remote: Ruth Barrera, Martin Hendry, and Ji Meng Loh
At SAMSI:Jogesh Babu, Pablo de la Cruz, Woncheol Jang, Tom Loredo, and Hyunsook Lee

Wed., 12 April

No meeting .

Wed., 19 April

Woncheol Jang: "Cluster Analysis of Massive Data with Application to Astronomy"
References mentioned

Remote: David Chernoff, Pablo de la Cruz, Martin Hendry, Tom Loredo, Haywood Smith, and Antonio Uribe
At SAMSI: Matthew Fleenor, Woncheol Jang, Ji Meng Loh, and Hyunsook Lee

Wed., 26 April

Ji Meng Loh: "Some Spatial Statistics for Astronomy" [Paper saving version]

Remote: Ruth Barrera, David Chernoff, Pablo de la Cruz, Ji Meng Loh, Tom Loredo, Haywood Smith, and Antonio Uribe
At SAMSI: Jogesh Babu and Hyunsook Lee

Wed., 3 May

Meeting Postponed .

Wed., 10 May

Tom Loredo:

Remote: David Chernoff, Pablo de la Cruz, Martin Hendry, Hyunsook Lee, and Tom Loredo
At SAMSI: Jogesh Babu, Jim Berger, Merlise Clyde, Bill Jeffreys, Woncheol Jang, and Ji Meng Loh,

References

Woncheol's recommendations

References from the second meeting (Feb. 15)

Reading materials for the third meeting (Feb. 22)

References from Mar. 8th meeting

Cross-Matching/Coincidence Assessment with the VO

References from Mar. 29th meeting
References from Apr. 5th meeting
References from Apr. 19th meeting

Group Members

Name Email Address Affiliation
Jogesh Babu Penn State University, Dept. of Statistics
Ruth Barrera National University of Colombia
Brendon Brewer University of Sydney, School of Physics
David Chernoff Cornell University, Dept. of Astronomy
Alanna Connors Eureka Scientific
Pablo de la Cruz Universitat de València, Dept. of Statistics
Gauri S. Datta University of Georgia, Dept. of Statistics
Sam Finn Penn State University, Center for Gravitational Wave Physics
Matthew Fleenor University of N. Carolina, Department of Physics & Astronomy
Martin Hendry University of Glasgow, Dept. of Physics & Astronomy
Angela Hugeback University of Chicago, Dept. of Statistics
Woncheol Jang Duke University, Dept. of Statistics
Kristofer Jennings Purdue University, Dept. of Statistics
Chunglee Kim Northwestern University
Hyunsook Lee Penn State University, Dept. of Statistics
Kuo-Ping Li University of North Carolina
Ji Meng Loh Columbia University, Dept. of Statistics
Tom Loredo Cornell University, Dept. of Astronomy
Vicent Martinez Universitat de València, Observatori Astronomic
Haywood Smith University of Florida, Astronomy Dept.
Antonio Uribe Observatorio Astronómico Nacional, National University of Colombia
Francisco Vera NISS
Martin Weinberg University of Massachusetts Amherst, Dept. of Astronomy
David Wittman University of California, Davis, Dept. of Astronomy