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

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 

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).
References in periodicals archive ?
A stratified sampling method that included strata construction and sample allocation provided more precise estimates than both simple random sampling and systematic sampling. Moreover, regressions between the MODIS-derived and TM-derived deforestation results provide precise estimates of both the total deforestation area and the deforestation distribution in each block.
Note that in Hobolth and Jensen (2002), circular systematic sampling on [0,1) instead of [0, 2[pi]) is considered, so Eq.
Using the 5 strata defined and systematic sampling within strata, we calculated a minimum sample of 84 boxes (17.3% occupancy rate) necessary to estimate occupancy with 50% precision compared to 75 boxes for a simple systematic design (17.4% occupancy rate) (Table 2).
Key words: acorn density; geostatistics; model-based inference; random sampling; semivariogram; stationarity; superpopulation model; systematic sampling; variance estimation.
If the variable or attribute is approximately evenly divided among members of the population, then we have a homogeneous population and we can use a simple sample design such as random or systematic sampling. If, on the other hand, the attribute is concentrated at different levels among different groups of the population, then we try to identify the groups and sample each group separately.
The county and diocesan archives take a back seat to the testamentary as it is her systematic sampling of more than 3,500 wills that forms the archival backbone of this monograph, the results of which are contained in an appendix of tables and graphs.
Systematic Sampling. Systematic sampling, like basic random sampling, requires that each transaction is assigned a reference number.
Regarding the past, International Atomic Energy Agency (IAEA) experts believed that systematic sampling and careful segregation of rods from particular parts of the reactor's core under its supervision would disclose how long the fuel had been burned and at what intensity.
A survey instrument designed to elicit the opinions, experiences, and perceptions of family physicians about DTCA was sent to a 2% (N = 880) systematic sampling of active physician members of the American Academy of Family Physicians.
Statistical process control (SPC) is, in effect, systematic sampling to determine and correct conditions that result in out-of-spec product.
I would have preferred to hear from a wider, more systematic sampling of residents, even at the cost of hearing from fewer working poor.
The author maintains that a systematic sampling was used but the modifications were made to include members from different years and with different authority, and then the stratification was done on an urban-rural basis.

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