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Date:         Wed, 23 Feb 2005 15:24:58 -0800
Reply-To:     cassell.david@EPAMAIL.EPA.GOV
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "David L. Cassell" <cassell.david@EPAMAIL.EPA.GOV>
Subject:      Re: Multiple Imputation--Missing Data
Comments: To: "Nick ." <>
In-Reply-To:  <>
Content-type: text/plain; charset=US-ASCII

"Nick ." <> wrote to me personally: > I found out why SAS was not imputing. In PROC MI when listing the > inputs (in VAR statement) one MUST also include the left hand side, > i.e. the Y along with the inputs X1, X2, X3, etc. I still get the > same error as before. Also, I look at some of the imputed values and > they are absolutely false! How can SAS look at an input, say home > market value, which ranges from $0 to $1 million+, and impute a > missing value as negative, like, $-235,567.345? Anyway. My previous > questions still stand. Thanks ...

This is the problem David Neal and I were talknig about the other day. If you use the defaults, SAS will fit distributions which are likely to be inappropriate. You have a distribution of market values which (in this context) will not ever go down below zero. (I assume.) But you don't get that truncation if you implicitly let SAS fit a normal distribution to your data. You have to make sure that a meaningful distribution of values gets used. In the worst case, you end up doing as Dale McLerran has discussed in SAS-L and fitting your own distribution to the data and then letting PROC MI impute from there. (You can look up Dale's code in the SAS-L archives.)

Unfortunately, PROC MI in SAS 8.2 (as you are using) is not as sophisticated as later versions. So you don't have the flexibility that appears in SAS 9.0 or SAS 9.1 .

HTH, David -- David Cassell, CSC Senior computing specialist mathematical statistician

"Nick ." <> wrote on 02/23/2005 11:48:34 AM:

> David,

> NICK > -- > ___________________________________________________________ > Sign-up for Ads Free at > >

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