Random Sampling: From 1 Different Sources
The sampling process whereby each unit in the population has an equal chance of being selected.
A procedure performed during a mother’s labour in which a blood sample is taken from a vein in the scalp of the FETUS. This enables tests to be performed that indicate whether the fetus is, for example, suffering from a shortage of oxygen (HYPOXIA). If so, the obstetrician will usually accelerate the baby’s birth.... fetal blood sampling
A method of diagnosing genetic abnormalities in a fetus using a small sample of tissue taken from the chorionic villi at edge of the placenta. Because the cells have the same chromosome makeup as those in the fetus, they can be used to detect genetic abnormalities. Chorionic villus sampling (CVS) is usually performed in the first 3 months of pregnancy in women who are at a higher-than-normal risk of having a child with a chromosomal disorder, such as Down’s syndrome, or a genetic disease, such as thalassaemia. Chromosome analysis of the villi cells takes place in the laboratory. CVS slightly increases the risk of miscarriage. choroid A layer of tissue at the back of the eye, behind the retina. The choroid contains many blood vessels that supply nutrients and oxygen to the retinal cells and to surrounding tissues in the eye. choroiditis Inflammation of the choroid. It is often caused by infections such as toxocariasis or toxoplasmosis, more rarely by sarcoidosis, syphilis, and histoplasmosis. It sometimes has no obvious cause. Treatment includes corticosteroid drugs for the inflammation, and antibiotic drugs for any causative infection.... chorionic villus sampling
A sample that is arrived at by selecting sample units such that each possible unit has a fixed and determined probability of selection.... random / random sample
The tendency for the estimated magnitude of a parameter (e.g. based upon the average of a sample of observations of a treatment or intervention effect) to deviate randomly from the true magnitude of that parameter. Random variation is independent of the effects of systematic biases. In general, the larger the sample size, the lower the random variation of the estimate of a parameter. As random variation decreases, precision increases.... random variation / random error
The procedure of selecting a number of subjects from all the subjects in a particular group or “universe”.... sampling
a subgroup of a total population selected by a random process ensuring that each member of the population has an equal chance of being included in the sample. It is sometimes stratified so that separate samples are drawn from each of several layers of the population, usually on the basis of age, sex, and socio-economic group. Selection is sometimes facilitated by identifying, in advance, certain units (e.g. towns or neighbourhoods) that will together represent the whole (a so-called sampling frame).... random sample
see random sample.... sampling frame
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