Network driven sampling; a critical threshold for design effects
32 mins 10 secs,
123.02 MB,
iPod Video
480x270,
29.97 fps,
44100 Hz,
522.16 kbits/sec
Share this media item:
Embed this media item:
Embed this media item:
About this item
| Description: |
Rohe, K( University of Wisconsin-Madison)
Friday 15th July 2016 - 14:00 to 14:30 |
|---|
| Created: | 2016-07-20 14:48 |
|---|---|
| Collection: | Theoretical Foundations for Statistical Network Analysis |
| Publisher: | Isaac Newton Institute |
| Copyright: | Rohe, K |
| Language: | eng (English) |
| Distribution: |
World
(downloadable)
|
| Explicit content: | No |
| Aspect Ratio: | 16:9 |
| Screencast: | No |
| Bumper: | UCS Default |
| Trailer: | UCS Default |
| Abstract: | Web crawling and respondent-driven sampling (RDS) are two types of network driven sampling techniques that are popular when it is difficult to contact individuals in the population of interest. This paper studies network driven sampling as a Markov process on the social network that is indexed by a tree. Each node in this tree corresponds to an observation and each edge in the tree corresponds to a referral. Indexing with a tree, instead of a chain, allows for the sampled units to refer multiple future units into the sample. In survey sampling, the design effect characterizes the additional variance induced by a novel sampling strategy. If the design effect is D, then constructing an estimator from the novel design makes the variance of the estimator D times greater than it would be under a simple random sample. Under certain assumptions on the referral tree, the design effect of network driven sampling has a critical threshold that is a function of the referral rate m and the clustering structure in the social network, represented by the second eigenvalue of the Markov transition matrix λ2. If m<1/λ22, then the design effect is finite (i.e. the standard estimator is n√-consistent). However, if m>1/λ22, then the design effect grows with n (i.e. the standard estimator is no longer n√-consistent; it converges at the slower rate of logmλ2). |
|---|---|
Available Formats
| Format | Quality | Bitrate | Size | |||
|---|---|---|---|---|---|---|
| MPEG-4 Video | 640x360 | 1.94 Mbits/sec | 468.19 MB | View | Download | |
| WebM | 640x360 | 620.8 kbits/sec | 146.34 MB | View | Download | |
| iPod Video * | 480x270 | 522.16 kbits/sec | 123.02 MB | View | Download | |
| MP3 | 44100 Hz | 249.76 kbits/sec | 58.90 MB | Listen | Download | |
| Auto | (Allows browser to choose a format it supports) | |||||