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Re: st: Re: multiple imputation and life tables


From   "Margaret Gassanov" <gassanov.1@osu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: multiple imputation and life tables
Date   Sat, 24 Jun 2006 11:06:14 -0400 (EDT)

Wonderful, thank you for your clarification.  I will try that.


> Margaret,
>
> (1) _i is the observation number and _j is the imputation number then
> my imp=_j.
>
> (2) Manually average over the imputed set. You will have 5 life-tables
> then collapse them into 1 taking average. This is only for statistics,
> for standard-errors you have to use Rubin's formula (webpage).
>
> (3) The options were for my example only. su=survival rate and
> h=hazard rate.
>
> R.
>
> ----- Original Message -----
> From: "Margaret Gassanov" <gassanov.1@osu.edu>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Saturday, June 24, 2006 8:52 AM
> Subject: Re: st: Re: multiple imputation and life tables
>
>
> Hi Rodrigo,
>
> Thank you for your reply.  I am having trouble understanding the formula
> you've provided.  More specifically, I'm not sure what the variable "imp"
> is in my dataset.
>
> After running the ice procedure, I have two new variables in my dataset:
> _i -- which gives a value of 5 for each case
>
> and
>
> _j
>
>  tab _j
>
>   imputation |
>       number |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>            1 |      1,075       20.00       20.00
>            2 |      1,075       20.00       40.00
>            3 |      1,075       20.00       60.00
>            4 |      1,075       20.00       80.00
>            5 |      1,075       20.00      100.00
> ------------+-----------------------------------
>        Total |      5,375      100.00
>
> Are you referring to one of these variables?
>
> Do I manually average each of the values from each of the imputations to
> obtain the correct final values?
>
> Also, what are the options "su" and "h"?
>
> Thank you for your help!
> Margaret
>
>
>
>
>> Margaret,
>>
>> Multiple Imputation (MI) allows you to deal with missing values.
>> The "solution" is that you will change your missing values for
>> several "possibles" values. For example if x has only one missing,
>> then MI creates 5 possible values for this missing, that's the
>> reason why you have N*5 number of observations.
>>
>> Then you change your N-1 dataset (assuming only 1 missing
>> value) for N*5 dataset. The statistical support is based on
>> Bayesian ideas and you can google MI to learn more on that.
>>
>> In your case you have to "run" the ltable command conditional
>> to the set imputed. If imp is the variable that describes the
>> # of imputation type
>>
>> forvalues i=1/5 {
>> ltable...  if imp==`i', su h
>> }
>>
>> Then your statistics (beg total, deaths, lost and rates) should
>> be averaged over the 5 tables. You should compute the
>> standard errors for these numbers and the formula is in
>> Joe Schafer's webpage: http://www.stat.psu.edu/~jls/mifaq.html
>> (see the question: How do I combine the results across the
>> multiply imputed sets of data?)
>>
>> I hope this helps you
>> Rodrigo.
>>
>>
>>
>> ----- Original Message -----
>> From: "Margaret Gassanov" <gassanov.1@osu.edu>
>> To: <statalist@hsphsun2.harvard.edu>
>> Sent: Friday, June 23, 2006 4:15 PM
>> Subject: st: multiple imputation and life tables
>>
>>
>> Hi,
>>
>> I'm new at multiple imputation (using the "ice" command), and I would
>> appreciate any help you can offer.
>>
>> I've made 5 imputed datasets for an event-history analysis I am doing.
>> I
>> want to use the ltable command to get hazard rates and survival rates,
>> but
>> ltable is not supported by micombine.  Thus, my output has the 1075*5 =
>> 5375 cases instead of the 1075 cases in the original dataset.
>>
>> The rates would still be accurate (correct me if I'm wrong), but the
>> "beginning total", "deaths", and "lost" numbers are not.  Does anyone
>> have
>> suggestions on how to obtain the actual numbers for these three columns
>> of
>> data?
>>
>> Thank you,
>> Margaret
>> *
>> *   For searches and help try:
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>>
>>
>
>
> I try to take one day at a time -- but sometimes several days attack me at
> once. -Jennifer Unlimited-
>
>
> *
> *   For searches and help try:
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> *
> *   For searches and help try:
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>
>


I try to take one day at a time -- but sometimes several days attack me at
once. -Jennifer Unlimited-


*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



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