sampling (redirected from stratified sampling)

sampling /sam·pling/ (sam´pling) the selection or making of a sample.

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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.

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sampling

the process of selecting a sample.

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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.

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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).

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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.