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22 Cards in this Set
- Front
- Back
population
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entire group of individuals about whom we hope to learn
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sample
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a representative subset of a population, examined in hope of leaning about the population
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Bias
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any systematic failure of a sampling method to represent the population is bias. impossible to recover from bias. errors include: voluntary response, undercoverage of the population, nonresponse bias, response bias
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randomization
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best defense against bias, each individual is give a fair, random chance to be selected
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matching
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attempt to force a sample to represent a population -- may make better samples but no substitute for randomizing
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sample size
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number of individuals in a sample. the sample size determines how well the pop is sampled, not what fraction of the population is sampled
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census
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a sample that includes the entire population
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population parameter
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numerically valued attribute of a population. attempt to estimate from sampled data.
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statistic, sample statistic
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values calculated for sample data. correspond to and thus estimate a pop parameter
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representative
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sample is representative if the statistics computed from it accurately reflect the population parameters
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Simple Random Sample (SRS)
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a sample when every element is the sampling frame had an equal likelihood of being chosen
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sampling frame
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list of individuals from whom the sample is drwan
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sampling variability
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natural tendency of randomly drawn samples to differ
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stratified random sampling
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pop is divided into several sub pop or strata, and the samples are drawn from each stratum. each stratum is homogeneous within and heterogeneous without.
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cluster sample
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entire groups or clusters are chosen at random. each cluster is heterogeneous within and homogeneous without and each one is representative of the population
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multistage sampling
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use of multiple sampling techniques
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systematic sampling
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people are chosen systematically from the sample (every tenth person on the list) and as long as it begins at a random point and there is no variables in the order of the list that would affect the sample, the sample can still be representative
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voluntary response bias
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introduced when participants can choose whether to participate. generally attracts those who are the extremes...those who feel strongly
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convenience sample
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introduces bias b/c the representative population is not all convenient to sample
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undercoverage
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sample with less representation than the pop
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nonresponse bias
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bias introduced when a large percent of people choose not to respond
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response bias
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anything in survey design that influences response is response bias: question wording, dress of surveyor
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