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Definition
selecting part of a population
(1) to represent some larger population of people or things
(2) to generalize from a sample to an unobserved population the sample is intended to represent |
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Definition
| those selected are not “typical” or “representative” of the larger population |
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| Equal probability of selection method |
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Definition
| all members of the population have an equal chance of being selected in the sample |
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Definition
| each element has an equal chance of being selected independent of any other event in the selection process |
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Term
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Definition
list of elements from which a probability sample is selected.
Ex: lists of licensed drivers, automobiles owners, welfare recipients |
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Definition
the range of sample estimates (mean)we will obtain if we select many samples.
Every increase in sample size improves the estimates of the mean because the sample means cluster more and more around the true population mean
Creates a normal or bell-shaped curve. |
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Term
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Definition
how closely the sample estimates will be distributed around the population parameter.
The sampling error is a function of the sample size – an inverse function.
As the sample size increases, the sampling error decreases
The sample will be more representative of the population |
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Term
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Definition
| The foundation of unbiased sampling.Assign a # to each element in the frame, not skipping any number in the process. A table of random numbers, or a computer program for generating them, is used to select elements for the sample. |
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Definition
| Choose all elements in the list for inclusion in the sample.select every 10th element for our sample. |
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| systematic sample with a random start |
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Definition
| selecting a random number between 1 and 10 to ensure against bias. The element having that number, plus every 10th element following it, is included in the sample |
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Term
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Definition
organize the population into homogeneous subsets (with heterogeneity between subsets) and select the appropriate number of elements from each.
To get a stratified sample of university students, we first organize our population by college class and then draw appropriate numbers of freshman, sophomores, juniors, and seniors. |
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Term
| Disproportionate Stratified Sampling |
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Definition
Select a number disproportionate to their representation in the population = oversample rare cases.
Ex: Because crime victimization for robbery or rape is relatively rare on a national scale, persons who live in large urban areas, where serious crime is more common, are disproportionately sampled. |
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Term
| Multistage Cluster Sampling |
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Definition
(1)The list of primary sampling units is compiled.
(2)A sample of those units is selected.
(3)The list of secondary sampling units is then sampled, and the process continues. |
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| Relying on available subjects – stopping people at a street corner |
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Term
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Definition
To select a sample on the basis of our own knowledge of the population, its elements, and the nature of our research goals;
Based on our judgment and the purpose of the study. |
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