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单词 sample
释义
sample

Mathematics
  • A subset of a population selected in order to make inferences about the population. (Strictly speaking, it is not a subset because elements may be repeated.) It is a random sample if it is chosen in such a way that every sample of the same size has an equal chance of being selected. If the sample is chosen in such a way that no member of the population can be selected more than once, this is sampling without replacement. In sampling with replacement, an element has a chance of being selected more than once. A quota sample is a sample in which a predetermined number of elements have to be selected from each category in a specified list. See also stratified sample.


Statistics
  • A subset of a population usually chosen in such a way that it can be taken to represent the population with respect to some characteristic, for example, height, or cost, or gender, or make of car. A list of members of the population of interest is called the sampling frame. If each member of the sample is selected by the equivalent of drawing lots, the sample is a simple random sample or, commonly, a random sample. In this case each sampling unit, i.e. each member of the population, has the same probability of being in the sample, independently of whether any other object is in the sample, and so all possible samples are equally likely. When the sampling units are people, the sample is often referred to as a sample survey. Various modifications of the simple random sample are often used. See cluster sampling; quota sampling; stratified sampling; systematic sampling.


Chemical Engineering
  • A small part or portion of a larger quantity of a product used to evaluate product quality. The sample is intended to be a representative part of the larger quantity. Statistical methods can be used to determine statistical variability of the sample from which judgements can be made such as for quality control purposes. Data of process variables such as temperature, pressure, flow, and level are used in the computer control of processes. A sample interval is the time between the gathering of information or data. In some cases, the time interval is very small such that the flow of information is virtually instantaneous whereas in others, the time interval is much greater.


Economics
  • A selection of examples of a class of objects, whose characteristics are used to infer those of the whole class or population. Sampling is used where it would be impossible, too slow, or too costly to examine the entire population. Inference from sample to population constitutes the subject matter of statistics. See also quota sample; random sample; stratified sample.


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