2005 Census Survey of Maricopa County, Arizona Household Survey

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Census Survey of Maricopa County, Arizona
Sample Design October 7, 2004 Dennis Schwanz,
U.S. Census Bureau
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2005 Census Survey of Maricopa County
Household Survey

• Sample Sizes
• Expected Accuracy
• Sample Size Assumptions

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Household Survey Sample Sizes
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Expected Accuracy of Household Survey Estimates

• Population estimate will be subject to sampling
  error (random variation in sample estimates
  compared to the actual estimate)
• Specifically, designed to have a margin of error
  (1 standard error)
• 1 of survey estimate

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• 95 confidence interval
• survey estimate 2 standard errors
• survey estimate 2 of survey estimate
• This means there is a 95 chance the actual total
  population estimate will be in this interval

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• In other words, this means that 19 out of 20
  times, the estimated population from the sample
  will be within 2 percent of the actual
  population.
• 99 confidence interval
• survey estimate 2.6 standard errors
• survey estimate 2.6 of survey estimate

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Household Survey Sample Size Assumptions

• The sample sizes were based on four
• assumptions
• Variation in Household Size
• - the more the variation the larger the sample
  size needs to be
• - 2000 Census household size variation estimates
  used
• - more accurate estimates if less variation in
  2005
• - less accurate estimates if more variation in
  2005

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• Vacancy Rate
• - the higher the vacancy rate the larger the
  sample size needs to be
• - 2000 Census vacancy rate used
• - more accurate estimates if vacancy rate
  lower in 2005
• - less accurate estimates if vacancy rate
  higher in 2005

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• Proportion of Total Housing Units in Sample
• - the higher the proportion in sample the
  smaller the sample size needs to be
• - the most current projected housing unit
  estimates used
• - more accurate estimates if actual housing
  unit total is lower than projection
• - less accurate estimates if actual housing
  unit total is higher than projection

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• Household Survey Response Rate
• - the higher the response rate the smaller the
  sample size needs to be
• - virtually 100 response rate assumed
• - less accurate estimates if response rate less
  than 100