Term
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Definition
| We observe and measure specific characteristics, but we don't attempt to modify the subjects being studied. |
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Term
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Definition
| We apply some treatment and then proceed to observe its effects on the subjects. |
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Term
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Definition
| Data are observed, measured, and collected at one point in time. |
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Term
| Retrospective or Case Control Study |
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Definition
| Data are collected from the past by going back in time (through examination of records, interviews, and so on). |
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Term
| Prospective or Longitudinal or Cohort Study |
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Definition
| Data are collected in the future from groups (called cohorts) sharing common factors. |
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Term
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Definition
| Occurs in an experiment when the experimenter is not able to distinguish between the effects of different factors. |
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Term
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Definition
| Members from the population are selected in such a way that each individual member has an equal chance of being selected. |
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Term
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Definition
| Size n subjects is selected in such a way that every possible sample of the same size n has the same chance of being chosen. |
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Term
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Definition
| We select some starting point and then select every kth (such as every 50th) element in the population. |
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Term
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Definition
| We simply use results that are very easy to get. |
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Term
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Definition
| We subdivide the population into at least two different subgroups (or strata) that share the same characteristics (such as gender or age bracket), then we draw a sample from each subgroup (or stratum). |
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Term
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Definition
| We first divide the population area into sections (or clusters), then randomly select some of those clusters, and then choose all the members from those selected clusters. |
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Term
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Definition
| The difference between a sample result and the true population result; such an error results from chance sample fluctuations. |
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Term
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Definition
| Occurs when the sample data are incorrectly collected, recorded, or analyzed (such as by selecting a biased sample, using a defective measurement instrument, or copying the data incorrectly). |
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