# Re: st: Which weight

 From "Sergiy Radyakin" <[email protected]> To [email protected] Subject Re: st: Which weight Date Mon, 8 Oct 2007 17:44:08 +0200

```Dear Steven,

there also a straightforward answer in the following situtations?

Situation A: N households were chosen at time t0 and followed as a
panel. M households were added to the panel at t1 (t0<t1). At any
point t I have crossectional weights and a probability to stay in the
sample for each household. At any moment t an event of interest can
happen in the houshold, (e.g. a child leaves the household). In this
case I add the characteristics of  the household at time t [and may be
t-1] to "my" sample). Which weights should I use? I obviously can't
choose weights at t0 because not all households were in the sample at
t0 and I can't use the weights at t1 because some of the households,
for which the event of interest has occured before t1, have dropped
out before t1 due to panel mortality.

Situation B: N households are chosen at time t0 and M households are
chosen at t1. pweights are given. However, during the time between t0
and t1, the population (e.g. the population of a country), from which
the samples were drawn has changed (e.g. doubled in size). I am
working with a pooled sample of households (N+M).  Which weights can I
use?
If I am working with one subpopulation only (e.g. men) and the
proportion of these cases has changed, can I still pool observations?
(E.g. women/men=50/50 in t0 but women/men=60/40 in t1). If yes, what
interpretation do I give to the estimates then? [this is not a panel
case]

Is there any good online guide on longitudinal weights? Preferrably
with plain examples on how to deal with different situations as
outlined above?

Thank you,
Sergiy

On 10/7/07, Steven Joel Hirsch Samuels <[email protected]> wrote:
> Nikkos, for a 'longitudinal' analysis like this, the general rule is
> to use the earliest weight. The sampling probability' is set when the
> unit is first selected.  The final weights differ from year to year
> because of post-stratification adjustments. To properly specify -
> svyset- you will need stratum and clustering information from the
> study documentation.
>
>
> Steven
>
>
> On Oct 7, 2007, at 7:06 AM, Nikolaos Kanellopoulos wrote:
>
> >
> > I have a dataset in wide format. I want to see the correlation
> > between x1
> > and x2 (the same variable in two different years). I want to use
> > weights to
> > correct for unequal sampling probabilities. Should I use the
> > weights of the
> > first year or the weights from the second?
>
>
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```