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Topic: Sampling


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In the News (Wed 17 Jul 19)

  
  Sampling (statistics) - Wikipedia, the free encyclopedia
Sampling is that part of statistical practice concerned with the selection of individual observations intended to yield some knowledge about a population of concern, especially for the purposes of statistical inference.
The sampling frame must be representative of the population and this is a question outside the scope of statistical theory demanding the judgement of experts in the particular subject matter being studied.
In survey sampling, many of the individuals identified as part of the sample may be unwilling to participate or impossible to contact.
en.wikipedia.org /wiki/Sampling_(statistics)   (1991 words)

  
 Introduction to Sampling   (Site not responding. Last check: 2007-10-22)
With nonprobability sampling, in contrast, population elements are selected on the basis of their availability (e.g., because they volunteered) or because of the researcher's personal judgment that they are representative.
Samples are evaluated primarily according to the procedures by which they were selected rather than by their final composition or size.
Studies with such samples are useful primarily for documenting that a particular characteristic or phenomenon occurs within a given group or, alternatively, demonstrating that not all members of that group manifest a particular trait.
psychology.ucdavis.edu /rainbow/html/fact_sample.html   (2255 words)

  
 Statistics Glossary - Sampling
Random sampling is a sampling technique where we select a group of subjects (a sample) for study from a larger group (a population).
When we sample a population with several strata, we generally require that the proportion of each stratum in the sample should be the same as in the population.
Sampling variability refers to the different values which a given function of the data takes when it is computed for two or more samples drawn from the same population.
www.cas.lancs.ac.uk /glossary_v1.1/samp.html   (1270 words)

  
 Samples and populations
A sampling frame can be one of two things: either a list of all members of a population, or a method of selecting any member of the population.
The essential principle of random sampling is that everybody in the population to be surveyed should have an equal chance of being questioned.
The bowl of soup is the population, and the spoonful is the sample.
www.audiencedialogue.org /kya2a.html   (6791 words)

  
 [No title]   (Site not responding. Last check: 2007-10-22)
Sample surveys attempt to determine the opinions, beliefs, behavior, or other parameters of a population of people from the responses of a sample from the population to a questionnaire or interview.
A probability sample is a sample drawn using a random mechanism to select the units from the frame to comprise the sample; that is, whether each unit in the frame is in the sample is a random event, with a specified probability.
Sample surveys tend to suffer to various extents from nonresponse bias, which is caused by systematic differences in the variables studied between the individuals who participate willingly in the survey and those who elect not to participate.
www.stat.berkeley.edu /users/stark/SticiGui/Text/ch16.htm   (6891 words)

  
 AuditNet: Free Resources for Auditors   (Site not responding. Last check: 2007-10-22)
Sampling and testing are commonly used terms to describe the process of obtaining information about an entire population by examining only a part of it.
When a sample is obtained statistically, it is possible to state, with a stipulated degree of confidence, that the number of errors in the sample applies proportionately to the unsampled portion of the universe as well.
Sample size and justification for expense or time spent are defensible as reasonable when confidence level desired is reasonable for the risk being evaluated.
www.auditnet.org /docs/statsamp.htm   (1907 words)

  
 PA 765: Sampling
In systematic sampling there is the danger of order bias: the sampling frame list may arrange subjects in a pattern, and if the periodicity of systematic sampling matches the periodicity of that pattern, the result may be the systematic over- or under-representation of some stratum of the population.
Repeated systematic sample has the side benefit that the variability in the subsample means for a given variable is a measure of the variance of that estimate in the entire sample.
The researcher seeks to identify variables where the sample mean deviates from the population mean, and speculates (preferably on the basis of prior literature) on the impact of such bias on the dependent variables of interest.
www2.chass.ncsu.edu /garson/pa765/sampling.htm   (4752 words)

  
 Survey Sampling Methods
Sampling error is the degree to which a sample might differ from the population.
Stratified sampling is often used when one or more of the stratums in the population have a low incidence relative to the other stratums.
Quota sampling is the nonprobability equivalent of stratified sampling.
www.statpac.com /surveys/sampling.htm   (742 words)

  
 Expertss.com
Sampling is usually done to achieve some efficiency in time, resources, and expense in an Organizational Survey project.
The purpose of sampling is the accomplishment of efficiency, representation, and minimal disruption.
The efficiency by which a survey sample is developed will depend on: internal skills in your company for data query and reporting, consolidation versus dispersion of relevant databases, data accuracy, and the extent to which there are multiple files with multiple data structures.
www.expertss.com /sampling.html   (1182 words)

  
 Sampling
Another reason for sampling is that not all units in the population can be identified, such as all the air molecules in the LA basin.
Non-probability samples are useful for quick and cheap studies, for case studies, for qualitative research, for pilot studies, and for developing hypotheses for future research.
Cluster sampling: cluster sampling views the units in a population as not only being members of the total population but as members also of naturally-occurring in clusters within the population.
www.csulb.edu /~msaintg/ppa696/696sampl.htm   (3066 words)

  
 Sample
Simple random sampling is the most basic: sample points are located, independently of each other, anywhere within the sampling region and all possible sample points have an equal probability of being selected.
One way to improve the sampling pattern is to overlay a regular array of cells, or a "grid," on the sample region and to select one or more samples within each cell.
Sample also records the sample coordinates and grid cell identifiers as attributes in the output shapefile.
www.quantdec.com /sample   (2193 words)

  
 Sampling   (Site not responding. Last check: 2007-10-22)
In a multistage random sample, a large area, such as a country, is first divided into smaller regions (such as states), and a random sample of these regions is collected.
In the second stage, a random sample of smaller areas (such as counties) is taken from within each of the regions chosen in the first stage.
Then, in the third stage, a random sample of even smaller areas (such as neighborhoods) is taken from within each of the areas chosen in the second stage.
www.stat.yale.edu /Courses/1997-98/101/sample.htm   (589 words)

  
 Chapter 11 sampling
While sampling technology has been available for a long time, only in the last decade has the speed of computers and availability of cost effective hardware made sampling with digital recorders the standard in the industry.
High sample rates are better at capturing high frequency waveforms, but if you are sampling lower frequency sounds, such as kick drum, bass, etc., you might consider sampling at the lower rate to save hard drive space.
At a sample rate of 22,050 Hz, the formula would be half that of 44.1 kHz...around 2.5 megs a minute or 5 megs a minute in stereo.
csunix1.lvc.edu /~snyder/2ch11.html   (1616 words)

  
 Statistics Glossary - sampling
Two samples in which the members are clearly paired, or are matched explicitly by the researcher.
Those samples in which the same attribute, or variable, is measured twice on each subject, under different circumstances.
It is also used when a random sample would produce a list of subjects so widely scattered that surveying them would prove to be far too expensive, for example, people who live in different postal districts in the UK.
www.stats.gla.ac.uk /steps/glossary/sampling.html   (1219 words)

  
 Sampling in Research   (Site not responding. Last check: 2007-10-22)
Sampling is the procedure a researcher uses to gather people, places, or things to study.
Samples are always subsets or small parts of the total number that could be studied.
The sampling distribution is a hypothetical device that figuratively represents the distribution of a statistic (some number you've obtained from your sample) across an infinite number of samples.
faculty.ncwc.edu /toconnor/308/308lect03.htm   (1693 words)

  
 On Near-Uniform URL Sampling
The approach of sampling from NEC query logs leaves questions as to the statistical appropriateness of the sample, as well as questions about the repeatability of the test by other researchers.
One goal of a random sampling approach is variability; that is, one should be able to repeat the sampling procedure and obtain different random samples for different experiments.
Although the distributions for the samples differ somewhat from that of the original graph, the differences are minor, and are due to the variation inherent in any probabilistic experiment.
www9.org /w9cdrom/88/88.html   (7357 words)

  
 Nyquist's Sampling Theorem   (Site not responding. Last check: 2007-10-22)
Suppose we are sampling a sine wave (Fig 6.3.
Now if we sample at twice the sample frequency, i.e Nyquist Rate, we start to make some progress.
An alternative way of viewing thr waveform (re)genereation is to think of straight lines joining up the peaks of the samples.
www.cs.cf.ac.uk /Dave/Multimedia/node149.html   (136 words)

  
 Sampling Systems   (Site not responding. Last check: 2007-10-22)
A special range has been developed for pharmaceutical sampling to meet the latest GMP and FDA guidelines.
Both powder samplers and liquid samplers are available in our unit dose sampling range.
This website, its code and contents is ©2002 Sampling Systems Ltd. All photography is ©2002 Sampling Systems Ltd. The Sampling Systems logo and associated animation is ©2002 Sampling Systems.
www.sampling.co.uk   (233 words)

  
 Signal Sampling and Reconstruction   (Site not responding. Last check: 2007-10-22)
A continous-time signal x(t) is sampled at a frequency of
there is no loss of information in sampling.
To explore sampling and reconstruction, select a signal or use the mouse to draw a signal x(t) in the window below.
www.jhu.edu /~signals/sampling   (107 words)

  
 School of Library, Archival and Information Studies -- UBC
Sampling [from Educational Research: Quantitative and Qualitative Approaches, by Burke Johnson and Larry Christensen]
Sampling Guide [available in English, French, and Spanish]
Statistical Inference: Populations, Samples, Estimates, and Repeated Sampling
www.slais.ubc.ca /resources/research_methods/sampling.htm   (200 words)

  
 Tektronix: Products > Oscilloscopes > CSA8200 / TDS8200 Sampling Oscilloscopes   (Site not responding. Last check: 2007-10-22)
Tektronix » Products » Oscilloscopes » CSA8200 / TDS8200 Sampling Oscilloscopes
For the most accurate results, use the 8200 Series as the golden reference for characterization and conformance test of emerging high-speed computer and communications electrical and optical signals:
Tektronix oscilloscope software, probes and accessories allow you to adapt your oscilloscope to your specific application needs and environment.
www.tek.com /Measurement/scopes/index/prodindex_sampling.html   (235 words)

  
 sampling Computer Encyclopedia Enterprise Resource Directory Complete Guide to Internet   (Site not responding. Last check: 2007-10-22)
sampling Computer Encyclopedia Enterprise Resource Directory Complete Guide to Internet
The process of taking a {sample} of a signal at evenly spaced intervals of time.
This is the first step in {Digital Signal Processing}.
www.jaysir.com /computer-encyclopedia/s/sampling-computer-terms.htm   (44 words)

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