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Re: st: Multiple imputation showing missing values during imputation


From   "Nailing Xia" <nailingxia@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Multiple imputation showing missing values during imputation
Date   Tue, 9 Dec 2008 17:13:54 -0500

Thanks, Michael. I checked the lower bound and upper bound variables
as well as the interval variables for cases that Stata report imputed
values being missing, but didn't find anything that looks strange. As
a matter of fact, those cases are within an interval (i.e., both the
lower bound and upper bound variables have a valid but different
value, indicating that the interval variable should be imputed within
that range) that needs an imputation with -intreg-.

And here're the details of the dataset: I am using a longitudinal
dataset that follows over 10,000 children for several years. The
dataset has 5 waves, and in the model I included over 8,000
individuals. The -ice- command includes around 50 variables in
total--as some of the variables are time-specific but some are not,
the total number of variables are around 200. Options I used with
-ice- include "sub", "passive", "cmd", and "interval". For all imputed
variables (including categorical variables), I use -regress- (except
for those that are included in the "interval" option and thus use
-intreg-"). In "interval" option, I included 21 variables (out of over
200 variables included in -ice-), and 15 of them have the imputed
value missing problem as described earlier. The number of missing
cases range from 1 to 49. What happens is that Stata will replace the
missing cases with mean and continue imputing. Then at cycle 6 when it
is imputing one of the variable that has the imputed value missing
problem, Stata shows that "convergence not achieved" and stops
imputing (although I am not sure whether this problem relates to the
imputed value missing problem).

If you know anything about this problem, please help. Thanks a lot!

Nailing Xia


On Tue, Dec 9, 2008 at 3:23 PM, Michael I. Lichter <mlichter@buffalo.edu> wrote:
> Nailing,
>
> I suspect that you haven't gotten any responses because your question is (or
> appears to be) very specific to your data, but you don't say much about the
> specifics of your data. It might be helpful to describe the variables
> involved and the constraints you are putting on the imputed data using the
> -interval- option to -ice-.
>
> Here's a stab in the dark, though. Is it possible that one or more of your
> interval variables are missing for two cases in which your variable redlun5
> is missing as well? If not, can you at least identify the two cases for
> which -ice- is failing to make an imputation and see if there is anything
> unusual about those cases' values on the other variables in the imputation?
>
> -ml
>
> Nailing Xia wrote:
>>
>> Hi,
>>
>> I am using -ice- for multiple imputation, and during the imputation
>> process, Stata shows that values for several imputed variables that
>> should have been imputed in previous cycle are actually missing. The
>> actual error message reads as: "I found that 2 missing value(s) of
>> redlun5 that should have been
>> imputed were missing at cycle 2. Replacing value(s) with mean, dumping
>> current data to file _ice_dump.dta and continuing."
>>
>> Anyone knows what seems to cause this problem? By the way, this
>> problem did not exist when I imputed without using the -interval-
>> option. But I checked my code for -interval- option, and it seems
>> fine.
>>
>> Many thanks!
>> Nailing Xia
>> *
>> *   For searches and help try:
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>> *   http://www.ats.ucla.edu/stat/stata/
>>
>
> --
> Michael I. Lichter, Ph.D.
> Research Assistant Professor & NRSA Fellow
> UB Department of Family Medicine / Primary Care Research Institute
> UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
> Office: CC 125 / Phone: 716-898-4751 / E-Mail: mlichter@buffalo.edu
>
> *
> *   For searches and help try:
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> *   http://www.ats.ucla.edu/stat/stata/
>
*
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