Dear Steven,
thanks for your reply. The short version of the answer is, (after going back to
documentation, even though it is not specifically mentioned): the survey seems
in fact to be stratified by geographical region in the country. There is no
mentioning of clustering. However, in order to obtain a longer time series, I am
also working with the same survey reduced to the capital city only that should
be unstratified.
So, given my original question (about how to test for the equality of variance
of my labor wage variable for the whole sample and for specific subgroups over
time, and for subgroups at the same point in time) help would be very
appreciated on both fronts, but ignoring strata for the moment is probably
easier.
Thanks in advance,
Johannes
PS: Here is the long answer: I am working with two survey series from Argentina,
the EPH. The full Argentinean survey is collected in urbean areas throughout the
country. The survey documentation is in Spanish only, and very unspecific about
sampling. The relevant section reads:
La E.P.H. es una encuesta por muestreo, desarrollada en aglomerados urbanos;
esto significa que para conocer las diversas características del total de los
hogares de un aglomerado urbano se encuesta una pequeña fracción representativa
de los mismos
Even though it is not mentioned specifically, the notion of representativeness
by urban area implies stratification. The full document can be found on
http://www.indec.mecon.gov.ar/dbindec/login.asp, using key
DF939RFEA45YLHN01DC1VK1G8W6T4J, going to "Base Usuaria Ampliada EPH - Puntual"
and following the link "El detalle de las bases disponibles se puede consultar
aquí".
As mentioned before, if I only use the series for one of the urban areas, there
is no stratification left.
There is no mentioning of clustering, but it does not specifically state random
sampling either.
Steven Samuels
<ssamuels@alban
y.edu> To
Sent by: statalist@hsphsun2.harvard.edu
owner-statalist cc
@hsphsun2.harva
rd.edu Subject
Re: st: How to test for equality of
variance in data with sampling weights
05/22/2007
09:38 AM
Please respond
to
statalist@hsphs
un2.harvard.edu
On May 26, 2007, at 9:16 AM, Johannes Metzler wrote:
I am working with household survey data, where the sample is not
clustered, not
stratified, but has sampling weights. Ultimately, I would like to
test the
equality of the variance of my labor wage variable...
___________________________________________
Johannes:
Can you please give some more detail about the sampling design?
Please include information about the target population and sampling
procedure, whether the same households appeared more than one time in
the survey, and how the weighting was done. A URL reference to the
original methodology document, hopefully in English, would be
sufficient. If necessary, send the document to me privately.
I have never encountered a houshold survey that was not done in at
least two stages, and I have never seen a national or regional survey
which was not stratified in some way. Without being sure of your set
up, I am reluctant to try to answer your question.
Steven
----- Forwarded by Johannes Metzler/Person/World Bank on 05/17/2007 09:45 AM
-----
Johannes
Metzler
To
05/16/2007 statalist@hsphsun2.harvard.edu
08:24 PM cc
35070 LCSPP
Subject
How to test for equality of variance in
data with sampling weights
Dear statalist users,
I am faced with a problem for which I have not been able to find a solution yet,
neither in statalist archives nor through googling, (even though it does not
strike me as something extremely fancy that I am trying)
I am working with household survey data, where the sample is not clustered, not
stratified, but has sampling weights. Ultimately, I would like to test the
equality of the variance of my labor wage variable
1) for the whole sample and for specific subgroups (such as age groups) over
time
2) for subgroups at the same point in time.
I am aware of the command "robvar" but
a) it does not feature weights
b) I am wondering if it is statistically appropriate to pool my data for two
years and specify 'year' as the groupvar in the by() option.
What would you advise me? Is there another command implemented?
Thank you very much in advance,
Johannes
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