sampling

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Related to cordocentesis: chorionic villus sampling, fetoscopy

sampling

the selection of part of a total population of consumers or products whose behaviour or performance can be analysed, in order to make inferences about the behaviour or performance of the total population, without the difficulty and expense of undertaking a complete census of the whole population.

Samples may be chosen randomly, with every consumer or product in the population having an equal chance of being included. Random samples are most commonly used by firms in QUALITY CONTROL where they are used as a basis for selecting products, components or materials for quality testing.

Alternatively, samples may be chosen by dividing up the total population into a number of distinct sub-groups or strata, then selecting a proportionate number of consumers or products from each sub-group since this is quicker and cheaper than random sampling. In MARKETING RESEARCH and opinion polling, quota sampling is usually employed where interviewers select the particular consumers to be interviewed, choosing the numbers of these consumers in proportion to their occurrence in the total population.

Samples may be:

  1. cross-sectional, where sample observations are collected at a particular point in time, for example data on company sales and the incomes of consumers in the current year, embracing a wide range of different income groups, as a basis for investigating the relationship between sales and income;
  2. longitudinal, where sample observations are collected over a number of time periods, for example data on changes in company sales over a number of years and changes in consumer incomes over the same time periods, as a basis for investigating the relationship between sales and income. See STATISTICAL INFERENCES, QUESTIONNAIRE.
References in periodicals archive ?
Obstetricians use various methods to attain fetal cells for diagnosis, including chorionic villus sampling (CVS), amniocentesis (AC), and cordocentesis (CC).
A second cordocentesis and chorionic villi analysis were contemplated to search for eventual metabolic disorders; blood tests were concordant with results obtained from the first examination.
Newer alternatives were being searched for noninvasively diagnosing fetal anemia as the traditional methods of amniocentesis and cordocentesis had a risk of complications like feto-maternal hemorrhage and fetal loss.
Intravascular fetal blood transfusion by cordocentesis represents a significant therapeutic advance for red blood cell isoimmunization, or hemolytic disease of the newborn.
Rh disease: Intrauterine intravascular fetal blood transfusion by cordocentesis. Turkish J Pediatr 1999;41:61-65.
Hemorragia fetai Sangrado hacia ia cavidad uterina: puede ocurrir por disrupcion accidentai dei cordon umbiiicai durante una amniocentesis o cordocentesis. Tambien cuando ia incision de una cesarea pasa a traves de una piacenta anterior.
Robustness of factor assays following cordocentesis in prenatal diagnosis of haemophilia and other bleeding disorders.
El diagnostico prenatal se realizaba mediante la determinacion de la actividad coagulante e inmunologica de FVIII o FIX en sangre obtenida por cordocentesis entre las 18 y 20 semanas de gestacion (1, 10, 13-15).