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| = Survey Sampling = <<TableOfContents>> ---- == Sample Type == === Propability sampling === All members of a population have a non-zero chance to be contacted in a survey instrument. Traditional statistics rely on this assumption. Examples: * Administrative surveys * Surveys with random recruitment (as by random digit dialing) === Non-probability sampling === Some members of a population are certain to be contacted or not be contacted. Examples: * Panel surveys * River surveys (i.e. surveys with open recruitment, as by banner ads) ---- == Survey Allocation == Allocation is the distribution of sample size across domains. === Designing Domains === The key considerations are: * are some splits more important to others? * if studying military recruitment, then sex/gender is a strong split * what splits will be used for reporting? + what is the expected response rate? * if too few responses are expected from a domain, then splits should be reconsidered * what is the desired margin of error? === Stratified Allocation === Stratification is the process of dividing the population into discrete stratum, and then sampling from the strata. '''Equal allocation''' is taking the same number from each stratum. '''Proportional allocation''' is taking a number proportional to the size of that stratum. '''Neyman allocation''' is an optimization of a key measure's margin of error against cost. It assumes a fixed cost per contact. On the other hand, if cost is assumed variable, it becomes an '''optimal allocation'''. Note that, if all measures are equally varied, proportional allocation is essentially the same as a Neyman allocation. ---- == Sampling Methods == '''Simple Random Sampling''' ('''SRS''') is essentially sorting randomly and taking the first N cases. '''Stratified Random Sampling''' ('''STSRS''') is the above process applied to a stratified sample, using proportional allocation. '''Systematic sampling''' is any form of sampling that takes every Nth case from a list. The key is then how the list is ordered. ---- CategoryRicottone |
