[R] Package Survey

[Thomas Lumley]

On Sun, 23 Sep 2007, Rita Cristina Pinto Sousa wrote:
> I?m using the package survey to obtain the statistics, fundamentally the 
> variance estimates. Can you explain why do I obtain the same result with the 
> replicate weights (as.svrepdesign function), for a stratified sample, and 
> without the replicate weights? I don?t understand it?

Without as.svrepdesign() you get the Horvitz-Thompson standard error 
estimator for the total and linearization estimators for other statistics. 
For the total and the mean these agree exactly with the JKn estimator. 
For nonlinear statistics they do not agree exactly, although they are 
usually close.

 	-thomas




> Many thanks for your attention,
> Rita Sousa.
>
> ***************************************
> # Apuramentos IUTIC-E
>
> rm(list=ls())
>
> ano <- "2006"
>
> require(survey)
> options(survey.lonely.psu="remove")
>
> setwd("C:/INE/Estatística-DME/IUTIC-E/")
>
> #Read the DB
> base_npc <- 
> read.table(paste(getwd(),"/Dados/",ano,"/NPC",".txt",sep=""),sep="\t",dec=",",header 
> = T)
>
> base_npc[is.na(base_npc)]<-0
>
> #Universe information
> univ_npc <- 
> read.table(paste(getwd(),"/Dados/",ano,"/NPC_Univ",".txt",sep=""),sep="\t",dec=".",header 
> = T)
>
> names(base_npc) <- tolower(names(base_npc))
> names(univ_npc) <- tolower(names(univ_npc))
>
> base_npc <- merge(base_npc,univ_npc,by="estr_cor")
>
> #Só algumas variáveis
> #base_npc <- 
> base_npc[,c("npc","estr_cor","pond_npc","npc_univ","e_cuse","div1")]
>
> #Survey design
> desenho_npc <- 
> svydesign(id=~npc,strata=~estr_cor,weights=~pond_npc,fpc=~npc_univ,nest=T,data=base_npc)
>
> #Replicate weights
> desenho_npc_JK <- as.svrepdesign(desenho_npc,type="JKn")
>
> #Without replicate weigths
> svyby(~e_cuse,~div1,desenho_npc,svytotal,drop.empty.groups=FALSE,vartype=c("se","var","cvpct"))
> #With replicate weigths
> svyby(~e_cuse,~div1,desenho_npc_JK,svytotal,drop.empty.groups=FALSE,vartype=c("se","var","cvpct"))
> ******************************************
>
>
> Citando Thomas Lumley <tlumley at u.washington.edu>:
>
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Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle