Re: Accounting for different sampling areas over different years [message #4202 is a reply to message #3825] |
Thu, 16 April 2015 13:08 |
mmr-UMICH
Messages: 21 Registered: February 2015 Location: A2, MI
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Strata are consistent across surveys for a country indicates that the codes/values of strata variable (after combining region and residence variables) are the same across the survey waves (e.g, 2001, 2006, 2011). If country has 5 regions and urban/rural, so there are 10 strata codes (say, 1 to 10) for each survey year. My understanding is that in pooled data set the number of strata is still to be 10. Because the stratification was the same but the sampling of clusters within stratum was different for each survey year, so cluster codes must be the different for identical strata across the survey waves. If we treat strata codes different across the surveys, the variance estimation is not only affected but also the degrees of freedom, confidence intervals, and p-value calculations.
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