A specimen of a whole entity small enough to involve no threat or damage to the whole; an aliquot.
cluster s.each sampling unit is a group of individuals.
end-tidal s.a s. of the last gas expired in a normal expiration, ideally consisting only of alveolar gas.
Haldane-Priestley s.an approximation of alveolar gas obtained from the end of a sudden maximal expiration into a Haldane tube.
probability s.each individual in the s. has a known, generally equal, chance of being selected.
Rahn-Otis s.an approximation of alveolar gas continuously provided by a simple device that admits just the latter part of each expiration.
random s.a selection on the basis of chance of individuals or items in a population for research; selection is made in such a way that all members presumably have the same chance of being selected.
stratified s.a subset of a total population, defined by some objective criterion such as age or occupation, is sampled.
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