LISTSERV at the University of Georgia
Menubar Imagemap
Home Browse Manage Request Manuals Register
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (February 2005, week 4)Back to main SAS-L pageJoin or leave SAS-L (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
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 ." <ni14@mail.com>
In-Reply-To:  <20050223194834.64D4F101D0@ws1-3.us4.outblaze.com>
Content-type: text/plain; charset=US-ASCII

"Nick ." <ni14@mail.com> 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 Cassell.David@epa.gov Senior computing specialist mathematical statistician

"Nick ." <ni14@mail.com> wrote on 02/23/2005 11:48:34 AM:

> David,

> NICK > -- > ___________________________________________________________ > Sign-up for Ads Free at Mail.com > http://promo.mail.com/adsfreejump.htm >


Back to: Top of message | Previous page | Main SAS-L page