February 21 Internal Validity

February 21 Internal Validity - February 21, 2008 External...

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February 21, 2008 External Validity (sampling) Lecture Overview: Population and sample The logic of sampling Sample size Probability samples Non-probability samples Population and Sample Research population consists of all elements that share a particular characteristic of interest Individuals (e.g.—students) Groups (e.g.—fraternities) Organizations (e.g.—universities) Texts (e.g.—news stories) Objects (e.g.—alcoholic beverages) Cases (e.g.—work-related injuries The sample consists of those elements of the population that are selected to participate in the study The sample is intended to allow researchers to test hypotheses about phenomena of interest within the population (generalizability) Sampling can provide reliable information at a smaller cost compared to using a census Data from a sample can be collected more quickly and more effectively (conserve resources) The Logic of Sampling A sample is said to be representative of the population from which it is drawn if a statistic
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February 21 Internal Validity - February 21, 2008 External...

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