Probably the weights are missing for cases in those regions, or they are
missing for some cases in such a way that the remaining cases have all the
same value and then the SD would be zero.
Weighting in SPSS means that each individual value is multiplied by the
weight before being counted. When the weight variable is missing for a case,
the multiplication has no result, and anything resulting from that procedure
would be missing. However, when some cases have missing weights and others
do not, the aggregation is carried out on the remaining cases. Since you do
not obtain any result, it is probably all the relevant weights that are
missing.
Hector
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of Tim
Pickles
Sent: 02 October 2009 12:09
To:
[hidden email]
Subject: Weighted SDs in Aggregate Command
Hi,
I am currently working on a geographical dental survey in which weights are
used for different regions/areas to counter the differing populations. I
therefore want to apply the relevant weight to the raw data and then
aggregate the data to give means, SDs, etc... of a number of different
variables. Unfortunately, the SD is often not generated for certain
variables in certain areas so, for example, 17 out of 22 areas have a SD
for age and the other 5 are just missing. Just to test, I took the
weighting off and rand the syntax again and all the SDs were generated
(though they were obviously meaningless) suggesting that applying the
weighting causes the problem.
Any ideas how I can resolve this problem?
Cheers,
Tim.
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