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| the entire group of individuals or instances about whom we hope to learn |
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| a (representative) subset of a population, examined in hope of learning about the population |
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| a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population, e.g. polls taken to assess voter preferences |
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| any systematic failure of a sampling method to represent its population; tend to over or underestimate parameters; almost impossible to recover from; examples include voluntary response, undercoverage, nonresponse bias, response bias |
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| each individual is given a fair, random chance of selection |
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| the number of individuals in a sample; sample size determines how well the sample represents the population, not the fraction of the population sampled |
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| a sample that consists of the entire population |
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| a numerically valued attribute of a model for a population |
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| Statistic, sample statistic |
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Definition
| values calculated for sampled data; those that correspond to, and thus estimate, a population parameter, are of particular interest |
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| a sample is said to be representative if the statistics computed from it accurately reflect the corresponding population parameters |
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| Simple Random Sample (SRS) |
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| a simple random sample of sample size n is a sample in which each set of n elements in the population has an equal chance of selection |
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| a list of individuals from whom the sample is drawn |
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| the natural tendency of randomly drawn samples to differ, one from another; not an error, a natural result from random sampling |
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| a sampling design in which the population is divided into several sub-populations called strata and random samples are then drawn from each stratum |
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| a sampling design in which entire groups, or clusters, are chosen at random; usually done for convenience, practicality or cost; clusters are heterogeneous |
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| sampling schemes that combine several sampling methods |
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| a sample drawn by selecting individuals systematically from a sampling frame; can be used when there is no relationship between the order of the sampling frame and the variables of interest |
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| a small trial run of a survey to check whether questions are clear; can reduce errors due to ambiguous questions |
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| bias introduced to a sample when individuals can choose on their own whether to participate in the sample; always invalid and cannot be recovered |
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| sample consists of the individuals who are conveniently available; often fail to be representative because every individual in the population is not equally convenient to the sample |
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| a sampling scheme that biases the sample in a way that gives a part of the population less representation than it has in the population |
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| bias introduced when a large fraction of those sampled fails to respond; those who do respond are likely to not represent the entire population |
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Definition
| anything in a survey design that influences responses, e.g. wording of questions, which may suggest a favored response |
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