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re: st: How to calculate standardized difference in means with survey weighted data?


From   "Ariel Linden. DrPH" <ariel.linden@gmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   re: st: How to calculate standardized difference in means with survey weighted data?
Date   Mon, 5 Mar 2012 11:47:53 -1000

Since my posting, Steve Samuels brought up the point that -pbalchk-
(-findit-) does not weight the sd as well as the means.

Mattieu Schonlau has a program that does balance checking that accounts for
survey weights and strata. I believe the progoram weights the sd
appropriately, but that needs to be verified.


net describe psbalance, from(http://www.schonlau.net/stata)

Ariel

'*********************************************************


You can use either -pstest-  or -pbalchk- (both are user written programs
-findit-).

Since they both allow for weights anyways, I assume you could use your
survey weight either in place of the existing weight needed to account for
multiple controls, or if need be, multiple the two weights together.

Ariel

Date: Sun, 4 Mar 2012 19:45:43 -0500
From: Lok Wong <lokwongedu@gmail.com>
Subject: st: How to calculate standardized difference in means with survey
weighted data?

I need to calculate the standardized bias (the difference in means divided
by the pooled standard deviation) with survey weighted data using STATA. 
I am comparing the means of 2 groups (Y: treatment and control) for a list
of X predictor variables. The purpose is to evaluate differences before and
after propensity score weighting (not matching so I cannot use PSMATCH2 or
other similar packages).

This is as far I got:

svy: mean X, over (Y)
estat sd
lincom [X]1 - lincom [x]0

I calculated the means by treatment/control groups.
Then obtained the standard deviations for each means (as the SE is reported
by svy: means) I used lincom to obtain the difference in means from the svy
post-estimation results.

How do I now extract the stored standard deviations for the 2 means, so I
can divide the difference in means by the pooled standard deviation?

I need to do this twice for 20 variables, so I don't want to just read the
output results and calculate by hand.

Any suggestions?

I did see an earlier posting (from 2005) on Standardized Response Mean, but
the suggested code (diff in change score / sd of change score) does not
address how to use survey weighted data.

Thanks!

Lok Wong Samson
Doctoral Candidate
JHSPH
lokwongedu@gmail.com


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