grab sample

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grab sample

In public health and medical statistics, a chaotic set of data from which conclusions are injudiciously drawn. Because the sample is not carefully randomized or scientifically selected, the conclusions derived from such sample groups may be inaccurate.

sample

1. a specimen of fluid, blood or tissue collected for analysis on the assumption that it represents the composition of the whole.

2. for statistical purposes a small collection of individual units taken from the population which is under investigation on the assumption that they represent the characteristics of the entire population.

EPSEM sample

acronym for 'equal opportunity of selection method'.

grab sample

sample of greasy wool taken at random by a special machine from each bale on the sale floor. Buyers price the bale on the basis of the appearance of the grab sample and the objective measurements.

multi-stage random sample

with very large populations it may be desirable to arrange the data into groups on one criterion, e.g. address by area of postcode, and to select randomly from within this group, then select from within this sample to obtain randomly a representative number of specimens, such as dogs of each age group.

random sample

the selection from a population of the units which are to constitute the sample of that population is made in such a way that each unit of the population has an equal chance of being selected. Called also simple random sample.

simple random sample

see random sample (above).

stratified random sample

the data is arranged into subsets or strata based on the possession of certain characteristics which are common to the members of the subset. The selection of units to comprise the sample of the parent population is arranged so that the proportional representation of each subset in the final sample fits a prearranged schedule.

volunteer sample

sample donated by interested parties; a biased sample because it does not represent all sections of the population. Called also self-selection.

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References in periodicals archive ?

Because grab samples were used for this evaluation, the authors would have been better served by evaluating unit performance by household, on the basis of four samples.