Dear John and Nick,
hoping to point out a useful reference on dealing with missing data
(continuous variables, namely), please find below the following one (I have
found it really useful in the recent past):
Briggs A, Clark T, Wolstenholme J and Clarke P. Missing....presumed at
random: cost-analysis of incomplete data. Health Economics 2003; 12: 377�392
Kind Regards,
Carlo
-----Messaggio originale-----
Da: [email protected]
[mailto:[email protected]] Per conto di Nick Cox
Inviato: mercoled� 17 settembre 2008 15.09
A: [email protected]
Oggetto: st: RE: Imputing values for an Index
This raises questions on several levels.
I am queasy at your tactic of finding a reference that supports what you
intend to do.
I don't think the alternative of saying that you can't do this if you have
missing values is that outrageous, but I don't know your context.
All methods of dealing with missing data other than going out and measuring
again -- when that is possible -- are deeply unsatisfactory, but some are
more deeply unsatisfactory than others.
There definitely are different takes but
1. I would impute upstream, and then do -pca-. If you do -pca- and then
impute, your interpretation problems seem even greater.
2. I would always compare results for complete observations and for complete
plus imputed to see what differences there are. You gain from knowing how
bad the problem is,
3. -impute- is among the lousiest ways to do this. -ice- (use -findit-) is
generally considered much better, it seems. I've never use it....
Nick
[email protected]
John Ataguba
I am implementing the -pca- command to generate an index of socioeconomic
status.� Stata will not provide values for any observation that is missing
in any variable when you use the -predict, score- after the -pca- command.
I decided to use the -impute- command to fill in the missing values of the
index.� Noting particularly that the missing values are not much and could
be assumed to be random.
My problem is that I need a valid reference to backup the process or to see
if there is a more neater way to get around this.
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