The advantage and disadvantage of implicitly stratified sampling

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Understanding Society Working Paper Series


Peter Lynn

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Explicit stratified sampling (ESS) and implicit stratified sampling (ISS) are alternative
methods for controlling the distribution of a survey sample, thereby potentially improving
the precision of survey estimates. With ESS, unbiased estimation of standard errors is
possible, whereas with ISS it is not. Instead, usual practice is to invoke an approximation
that tends to result in systematic over-estimation. This can be perceived as a disadvantage
of ISS. However, this article demonstrates that true standard errors are smaller with ISS
and argues that this advantage may be more important than the ability to obtain unbiased
estimates of the standard errors.

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