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.

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]

sampling

/sam·pling/ (sam´pling) the selection or making of a sample.
chorionic villus sampling  (CVS) any of several procedures for obtaining fetal tissue to use in prenatal diagnosis, performed at 9 to 12 weeks' gestation, usually by means of a catheter passed through the cervix or by a needle inserted through the abdominal and uterine walls.
percutaneous umbilical blood sampling  (PUBS) cordocentesis.

sampling

An MRI term for the conversion of analog signals to discrete digital values through a preselected measurement process.

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.

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]

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.

sampling

harvesting small amounts of tissue to allow laboratory microbiological culture and determine antimicrobial sensitivity; clinical samples should be taken before application of antiseptics/antimicrobial therapies; skin and nail scrapings are sealed in a labelled paper sachet; wound exudate samples (taken from the deepest part of wound) are transported in a sterile container; adequate amounts of the sample must be harvested, and include full clinical details (e.g. nature of sample, location, date of collection, patient biographical details, information of health status and current medications regime)

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).

sampling

the process of selecting a sample.

area sampling
dividing the population into equal areas and randomly selecting from among the areas.
cluster sampling
when the population to be sampled exists in clusters, e.g. herds, sampling can be done by random selection between the herds. This assumes that each cluster is a homogeneous group.
sampling fraction
ratio of the number of units in the population to the number of units in the population.
sampling frame
the names of the component parts of the population from which the sample is to be collected.
quota sampling
the sections of the population, e.g. milking cows, dry cows, yearlings, calves are represented in the sample in the same proportion as they exist in the population.
stratified sampling
a simple random selection is performed in each stratum of those created in order to permit a different sampling percentage to be used in each stratum.
systematic sampling
the sampling is random but the samples are drawn systematically, say every third unit, the first unit also being chosen randomly.
two-stage sampling
an example of multi-stage sampling. The first sampling is of large groups, e.g. herds, then a second-stage sampling is carried out within herds, e.g. sire families, with possibly a third stage, of individual cows within the sire families.
sampling units
individual members of a population. It is often difficult to define exactly what is a unit because of the design of the study.
sampling variation
the variation that occurs between samples of the one population. A measure of the random error of the sampling technique used.
References in periodicals archive ?
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.
Dividing the counts for each species by 121 (number of points/frame) gives the percent dominance of species within a sampling frame.
We derived population representativeness of the sampling frame by dividing the number of unique records by the September 30, 2008, VetPop2007 estimate of the women veteran population.
TABLE 1 Summary of SSI Study sampling frames Sampling Frame Percentage of Sample SSA RMA Catchment Area Interviewed Records Records Chicago 56.
It is easier to construct a sampling frame consisting of a complete list of structures, or units that may be turned into a complete list of elements when required.
It would seem that problem of tracing very small or new firms to keep up-to-date sampling frames would severely complicate these efforts.
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.
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.
Given a sampling frame consisting of Fortune 500 companies (a notoriously oversampled population) we consider this a more than acceptable rate.
The Register serves mainly as the sampling frame for various economic surveys conducted by the department.