Sampling

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Sampling
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Definition

• Choosing a relatively small number of cases, the
  study of which may tell us much about the larger
  population from which they have been selected.
• Time
• Cost
• Variability

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Why does Sampling Matter?

• From a practical perspective?

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Population

• Generalizability
• Census
• Not Just Surveys
• vs. Sample
• Cases

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Types of Samples

• Probability
• Representativeness

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Non-probability samples

• Probability of being selected?
• Self-Selection
• Convenience
• Purposive
• Snowball

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Probability samples

• We know the probability of being selected

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Non-Representative Samples

• Bias
• Systemmatic/Non-Systemmatic

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Representative Samples

• Major Attributes
• Quota

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Randomization

• Random number generator
• Simple Random
• Systematic Random
• Stratified sampling
• Cluster sampling

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The Central Limit Theorem
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Sampling Error
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Total Sampling Error

• Sampling bias
• Random Sampling Error

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Sampling Error

• Accuracy
• Margin of Error
• Confidence Interval

• Confidence
• Percentage
• Level