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Date:         Fri, 16 Sep 2005 17:12:22 +0930
Reply-To:     kylie.lange@flinders.edu.au
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Kylie Lange <kylie.lange@flinders.edu.au>
Subject:      Re: Missing values analysis
Comments: cc: bozena@pitt.edu
In-Reply-To:  <S180392AbVIOQ5W/20050915165728Z+110215@avas-mr11.fibertel.com.ar>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Bozena,

I think Hector may have slightly misunderstood what you are trying to achieve, but indirectly he has answered your question. My understanding (and Hector's as well from his reply) is that SPSS' imputation methods are completely deterministic - ie, the two cases with the same values on the observed variables will have the same imputed value, and additionally each time you run the imputation they will have the same imputed value. For multiple imputation (where a random error component is included in deriving the imputed value) the results will differ slightly, as you say. For that you will need a program that specifically implements a multiple imputation method.

For a list of multiple imputation software see http://www.multiple-imputation.com/.

Hopefully this helps, and others will chime in if I'm off track with anything here.

Cheers, Kylie.

On 16/09/2005 2:27 AM, Hector Maletta wrote:

>Bozena, >It might be that the second run takes into account the values imputed in the >first run, and this may be the cause of the difference. To avoid that, start >every time with the same untouched file, or copy the old variables under new >names before imputing valid values for old missing values. > >Hector > > > >>-----Original Message----- >>From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] >>On Behalf Of Zdaniuk, Bozena >>Sent: Thursday, September 15, 2005 1:38 PM >>To: SPSSX-L@LISTSERV.UGA.EDU >>Subject: Missing values analysis >> >>Hello, I am entering the unfamiliar territory so please >>forgive if my question is na´ve or parts of it incorrect. >>Question: Is there a way in MVA in spss to have multiple >>imputation of missing data? In other words, is it possible to >>run, let's say, a few EM runs with the same predicted and >>predicting variables in the syntax and get slightly different >>imputed values on each run? >>Thanks. >>Bozena >> >>Bozena Zdaniuk, Ph.D. >> >>University of Pittsburgh >> >>UCSUR, 6th Fl. >> >>121 University Place >> >>Pittsburgh, PA 15260 >> >>Ph.: 412-624-5736 >> >>Fax: 412-624-4810 >> >>email: bozena@pitt.edu >> >> >>-----Original Message----- >>From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] >>On Behalf Of Martin Sherman >>Sent: Thursday, September 15, 2005 10:53 AM >>To: SPSSX-L@LISTSERV.UGA.EDU >>Subject: Re: converting a missing time value into a real time value >> >>Hector: Thanks for the response. I tried using q1=9:00. and got an >>error message that the : was creating a problem. I will >>wait to see if >>anyone else responds. thanks again. martin >> >> >> >> >>>>>"Hector Maletta" <hmaletta@fibertel.com.ar> 09/15/05 10:49 AM >>> >>>>> >>>>> >>If you have only one case in that situation, you can issue >>the command as >>follows: >> >>IF (SYSMIS(Q1))q1=9:00. >> >>But you may have other cases with the time missing, and you >>may not want all of them assigned 9 hours. If it is so, you >>better allocate the new value based on the relevant case's ID: >> >>If (ID=93869)q1=9:00. >> >>I have not considered possible further complications arising >>from the fact that your variable is a date variable (in >>hours). The simple statement q=9:00 may not work, but I don't >>have time to go into that now. >> >>Hector >> >> >> >>>-----Original Message----- >>>From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] >>> >>> >>On Behalf >> >> >>>Of Martin Sherman >>>Sent: Thursday, September 15, 2005 11:43 AM >>>To: SPSSX-L@LISTSERV.UGA.EDU >>>Subject: converting a missing time value into a real time value >>> >>>Dear list, I have a time variable (HH.MM.SS) where a subject has it >>>missing (just a dot in the data field). I want to change >>> >>> >>it to 9:00. >> >> >>>I have tried the following but it doesn't work. >>>if q1 eq 52724937 @55time_ eq 9:00. >>>execute. >>>and I have tried the following and it doesnot work. >>>Is there a way I should be represented 9:00. Advice appreciated. >>> >>>if q1 eq 52724937 @55btime_ eq 9. >>>execute. >>> >>>martin sherman >>> >>>__________ Informacisn de NOD32 1.1217 (20050914) __________ >>> >>>Este mensaje ha sido analizado con NOD32 Antivirus System >>>http://www.nod32.com >>> >>> >>> >>> >>__________ Informaciˇn de NOD32 1.1217 (20050914) __________ >> >>Este mensaje ha sido analizado con NOD32 Antivirus System >>http://www.nod32.com >>


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