random sampling

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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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

ran·dom sam·pling

a selection of elements from a population such that each possible outcome is independent of other possible outcomes and the probability of each member of the population being chosen is equal.
Farlex Partner Medical Dictionary © Farlex 2012

ran·dom sam·pling

(ran'dŏm sam'pling)
A selection of elements by a formal randomizing device for purposes of inference about a population in such a way that the probability of each possible outcome may be precisely specified in advance; the inferences are necessarily stochastic.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
But in fact it's not quite that simple, and this is where the issue of random sampling comes in.
Using 5 minutes as the maximum acceptable patient waiting time until an interviewer becomes available, systematic random sampling resulted in an average of 9.0 percent of selected patients not being interviewed.
Thus it was suggested to include a large sample size for the small bias in ACS, as it happened in simple random sampling.
In this research article, we have proposed a class of ratio estimators using the known knowledge of the auxiliary variable such as population mean, population median, population coefficient of variation, population coefficient of kurtosis for finite population mean under maximum and minimum using simple random sampling. We have also find some theoretical conditions under which the suggested class of ratio-type estimators have always efficient than the Kadilar and Cingi [1] estimators.
Additional aliquots from six bottles of RM 8504, selected according to a stratified random sampling scheme, were analyzed by GC-ECD equipped with not only a DB-5 capillary column (described above) but also one with a relatively non-polar stationary phase (DB-XLB, J & W Scientific, Folsom, CA).
While quantitative researchers use complex mathematical formulae to make sample size considerations, and they promote the use of random sampling (even though the overwhelming majority of studies utilize non-random samples), sample size considerations in qualitative studies are neither mathematical nor systematic.
In particular, a new approach, called term-based random sampling, is introduced based on the Kullback-Leibler divergence measure.
The rider was banned after after testing positive for cocaine, as part of random sampling at Salisbury in September last year.
Users can choose the level of scanning they want to perform from a random sampling to a detailed examination.
3 WWW.GROUPHUG.US A random sampling from this disturbingly addictive confessional website: "Everyone thinks I've been a vegetarian for the past 8 years, but I'm not.
It has recommended that the US Department of Agriculture (USDA) test all high-risk cattle, such as those that die on farms or are too ill to walk, and also do random sampling of healthy cattle more than 30 months old.