sampling

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Related to purposive sampling: Snowball sampling

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 ?
Purposive sampling technique was used to sample 250 students from 42 ghetto secondary schools.
Hundred pupils from three semi-government and two private schools of district Peshawar were selected on the basis of purposive sampling technique.
The tehsil under study (Ramtek) was selected by purposive sampling. There are four aided and two government tribal schools located in this tehsil.
Based on purposive sampling and to include schemes of different sizes, type (new build, remodeled, private, public) and location, 35 ECH schemes were chosen from the Elderly Accommodation Council's 2008 directory.
Apart from the extensive research carried out for this book--focus group sessions in selected urban and rural parishes and a purposive sampling of adolescents in selected schools in Jamaica--Forbes brings her own rich experience as a media worker herself to bear on this subject (she and her husband started a multi-media production company in Jamaica in the early 1980s called Phase Three Productions).
Sample and Method: Purposive sampling technique was used.
The statements such as selection of cases is typically done by purposive sampling in case-control studies; estimates based on sample surveys are more accurate than those based on total enumeration; the only advantage of systematic sampling over random sampling technique is its simplicity; population is a group of individuals in the population are some such examples.
Purposive sampling is a type of sampling that selects specific individuals or groups because they match criteria that are necessary for the investigation of whatever is being studied.
The investigators used snowballing and purposive sampling (for geographic and demographic balance) to recruit participants.
Purposive sampling is frequently selected for obtaining data in qualitative research.
Buetow (University of Auckland) explains the primary health study designs, the need for literature reviews, purposive sampling strategies, and methods of presenting qualitative research findings.