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What Sample Density ?

What Sample Density ?. Tiny Useful for testing syntax Small Useful for quick test of idea Regular 1% sample (1 of 100 people) Most commonly used Large 5% sample (20 of 100 people) Necessary for small sub-groups. What Samples ? What Years ?. Design Considerations

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What Sample Density ?

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  1. WhatSampleDensity? • Tiny Useful for testing syntax • Small Useful for quick test of idea • Regular 1% sample (1 of 100 people) Most commonly used • Large 5% sample (20 of 100 people) Necessary for small sub-groups

  2. WhatSamples? WhatYears? Design Considerations • What is the research question? • Subject population = small sub-group 5% samples or multiple 1% samples Constraints of the Data: • Confidentiality / Geographic masking • Variables tied to specific samples

  3. WhatVariables? Look at the variable descriptions!! Is it available in all years? All samples? Check the Universe Statements

  4. CaseSelection: 1. During extract process • For permanent case exclusion • Saves space on your PC • Runs faster on IPUMS server • Doesn’t tie up our PC 2. On your PC • For variables without extract case-selection • Complex selections • For temporary case exclusion

  5. CaseSelection: • File Size Considerations: Optional for: Tiny, Small, Large (1%) samples Few Variables Recommended for: Large (5%) samples Many Variables • Design Considerations: • Selected cases only / include HH, family • “and” / “or” across variables

  6. DataQualityFlags: • Variable specific (in most cases) • Indicates some responses have been changed • “0” means that response is unchanged • all other values were changed • Explains why a new value was needed • illegible • internally inconsistent (record, household) • missing • Explains procedure used to derive new value • internal edit (record, household) • “hot deck” (match “donor” on personal characteristics) • “cold deck” (mean value of cases with valid response)

  7. UniverseStatements  Who was asked the question  in universe  in extract  Extract Cases  Universe + N/A  N/A  people not asked question  cases not in the universe  Cases with all other values are in the universe  Defines the demoninator

  8. When to Use Weights • ALWAYS • All samples have weights • Weights redistribute cases in some years • Weights inflate cases in all years

  9. Which Weight to Use? • HHWT for analysis seeking to make conclusions about households (must choose PERNUM=1) • PERWT for analysis seeking to make conclusions about individuals • SLWT for analysis that includes any sample line (SLWT adjusts for non-sample line years) • MIGSAMP use with 1980 migration variables

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