sampling

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sampling

 [sam´pling]
the selection or making of a sample.
the selection of a group of people, events, behaviors, or other elements that are representative of the population being studied in order to derive conclusions about the entire population from a limited number of observations.
accidental sampling a type of nonprobability sampling in which the population selected is easily accessible to the researcher; available subjects are simply entered into the study without any attempt at randomization. Called also convenience sampling.
chorionic villus sampling (CVS) sampling of chorionic villi from the villous area of the chorion, a procedure used for prenatal diagnosis at nine to 12 weeks of gestation. A catheter is inserted either through the cervix or through the abdominal wall and fetal chorionic villus tissue for analysis is aspirated under ultrasonic guidance. This has been used for the prenatal diagnosis of fetal trisomies, hemoglobinopathies, and biochemical disorders. It allows first trimester diagnosis and direct chromosomal and biochemical analysis but does not screen for neural tube defects or certain other anomalies; some of those may be identified by maternal serum and amniotic fluid alpha-fetoprotein measurements.
A diagram of the technique of transvaginal chorionic villus sampling. From Mueller and Young, 2001.
cluster sampling a type of probability sampling in which the population is divided into groups on the basis of some shared characteristic (such as hospitals grouped by geographic region) and a random sample is drawn from each of these groups.
convenience sampling accidental sampling.
nonprobability sampling sampling in which not every element of the population has an opportunity of being selected for the sample; the sample is not representative of the population and generalizations cannot be made to the population.
percutaneous umbilical blood sampling a procedure used to obtain fetal blood for examination; a sterile needle is inserted through the mother's abdomen and uterus, and guided to one of the umbilical veins via ultrasound. This procedure has begun to replace fetoscopy because it has a lower complication rate. Direct sampling of fetal blood provides more rapid test results than amniocentesis, and a more definitive diagnosis. It can be used to identify chromosomal abnormalities, detect a fetal infection, and assess fetal growth and development. Called also cordocentesis.
Percutaneous umbilical cord sampling, also known as cordocentesis. The needle is advanced through the skin and into the uterus. Once the needle punctures the umbilical cord and one of the uterine veins, cord blood is aspirated by the syringe. From Malarkey and McMorrow, 2000.
probability sampling sampling in which each element of a population has an opportunity of being selected for the sample; its purpose is to obtain a sample that is representative of the population and from which generalizations to the population can be made.
purposive sampling a type of nonprobability sampling in which the researcher consciously selects specific elements or subjects for inclusion in a study in order to ensure that the elements will have certain characteristics relevant to the study.
quota sampling a type of nonprobability sampling in which an accidental sample is adjusted to ensure that certain subgroups are not underrepresented; its purpose is to obtain a sample that is representative of the population to which the researcher wishes to make generalizations.
random sampling probability sampling.
stratified random sampling sampling in which the population is divided into several groups that are alike in certain ways and a random selection is made from each group.
systematic sampling the selection of study objects conducted when an ordered list of all members of the population is available; subjects are chosen from the list at a given uniform interval from each other, using a starting point that is selected randomly.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

sam·pling

(sam'pling),
The policy of inferring the behavior of a whole batch by studying a fraction of it.
[MF essample, fr. L. exemplum, taking out]
Farlex Partner Medical Dictionary © Farlex 2012

sampling

An MRI term for the conversion of analog signals to discrete digital values through a preselected measurement process.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

sampling

Statistics The obtaining of representative material from a population Surgery A procedure that obtains a soupçon of material for pathologic evaluation, without a formal attempt at complete removal of a suspected or confirmed lesion. See Cluster sampling, Inferior petrosal sinus sampling.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

sam·pling

(sam'pling)
The policy of inferring the behavior of a whole batch by studying a fraction of it.
[MF essample, fr. L. exemplum, taking out]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

sampling

  1. the act of taking a fraction of substance to be tested or analysed.
  2. the selection of some parts from a larger whole as in statistical sampling.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

sampling 

The selection of a group of subjects from a population. This is usually done for the purpose of experimentation. The part of the population selected is called the sample: it is usually considered to be representative of a given population. A good sample must be random, i.e. every possible member of that population has an equal chance of being selected. Otherwise, it is said to be biased. Sampling can extend either across geographical areas (spatial sampling) or over a period of time (temporal sampling).
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
(21) The methods discussed here would be insufficient to model data where subjects have hundreds or even millions of observations per observational unit in the sampling frame. However, the higher-level principle remains: We could estimate a model that segments the sampling frame into small number of groups, such that the sampling can be performed within each group.
CCHS collects information from respondents aged 12 and over, CTADS collects information from respondents aged 15 and over; the two surveys use different sampling frames; the annual sample for CTADS is 20,000 compared to 65,000 for CCHS; in CCHS, smoking questions are asked in the context of a wide range of health-related behaviours whereas in CTADS, all questions are related to the use of multiple products and substances with addictive properties." (6)
The images and software required for generating the sampling frame are freely available online, though the Google Earth and QGIS software took some time to learn.
Revisiting Table 2, the wage rates by industry were defined for the suburban fringe sampling frame. In suburban areas, the primary minimum-wage industry is Accommodation and Food Services (NAICS Code 72).
Dividing the counts for each species by 121 (number of points/frame) gives the percent dominance of species within a sampling frame. A chi-square analysis of the data shows that significant differences (p=0.006) in distribution occur among plant species among the three study areas.
To create the sampling frame, we added a data field in each database to identify the source database.
* Revising the sampling frame for existing household surveys in Thailand on the basis of the new pilot Censuses.
TABLE 1 Summary of SSI Study sampling frames Sampling Frame Percentage of Sample SSA RMA Catchment Area Interviewed Records Records Chicago 56.5 X X Detroit 70.8 X Los Angeles 72.8 X Seattle 72.7 X Portland 72.3 X Contiguous Northern 67.5 California Counties X X Total 67.8 - - Percentage of Initial Date of Selection Interviews from RMA and/or Conducted Catchment Area SSA Sample (a) Before 1/1/97 Chicago June 1996 28.8 Detroit November 1996 66.2 Los Angeles October 1996 8.9 Seattle October 1996 91.1 Portland July 1996 72.1 Contiguous Northern California Counties July 1996 52.8 Total - 55.6 (a) Date of Selection from RMA and/or SSA Sample refers to the date the SSI Study site used to identify its sample based on a beneficiary's SSI eligibility in a RMA or SSA database.
One important observation made by Heiden is that the "post 1996 sampling frame appears to be new and different from the old pre-1996 sample because its hospital members are on average much nearer to amusement parks than the old hospitals were, and serve potential patients who have different, higher propensity than potential ER patients in the pre-1997 NEISS sample, to use the parks that are the source of any potential injury reported to the agency."
O'Rourke, spend considerable time explaining the rationale for the NOS's sampling frame and the implications of the choices they made in designing it.
Second, budget limitations usually require limitations on the sampling frame, so that trainees and controls are followed only for a short period before and after training.
Only 8.5 percent of these establishments were dropped from this sampling frame due to incomplete address information, leaving a sampling frame of 583 private-sector, for-profit establishments.(3)