3A/3B Vocabulary

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population

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the entire group of individuals we want information about

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sample

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a subset of individuals in the population from which we collect data

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sample survey

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a study that collects data from a sample to learn about the population from which the sample was selected

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random sampling

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using a chance process to determine which members of a population are chosen for the sample

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observational study

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observes individuals and measures variables of interest, but does not attempt to influence the responses

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retrospective study

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observational study that examines existing data for a sample of individuals

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prospective study

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observational study that tracks individuals into the future

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experiment

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deliberately imposes treatments on experimental units to measure their responses

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simple random sample

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a sample chosen in such a way that every group of 𝑛 individuals in the population has an equal chance to be selected as the sample

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stratified random sample

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a sample selected by choosing an SRS from homogeneous subgroups and combining the SRSs into one overall sample