Posted by
Kylie on
Dec 20, 2012; 5:04am
URL: http://spssx-discussion.165.s1.nabble.com/R-and-R-square-over-90-for-regression-with-imputed-dataset-tp5717033p5717062.html
Hi,
For multiple imputation you should be running your regression on the entire imputed dataset (ie, the one with the original data and the 5 imputed datasets in it) - not just selecting out the 5th imputed dataset. With your datafile split by the Imputation_ variable (I think that is what is called - can't check at the moment, sorry), SPSS will detect that it is a multiply imputed dataset and analyse the data appropriately. Specifically, it will run your regression on each of the 5 imputed datasets and present results for each one separately plus a 'pooled' set of results. It is these pooled results that you want.
Hope this helps.
Cheers,
Kylie.
________________________________________
From: SPSSX(r) Discussion [
[hidden email]] on behalf of
[hidden email] [
[hidden email]]
Sent: Thursday, 20 December 2012 5:20 AM
To:
[hidden email]
Subject: Re: R and R square over .90? for regression with imputed dataset
Hi Rich and Art,
Thanks much for your responses. I actually found that there were 2 different
datasets produced by one MI attempt. One lists all variables generated by
all imputations - variables from the original, imputations 1~5. Since I have
about 150 cases, this lists have 150 x 5 imputations + 150 original data.
The other dataset has only 150 cases.
I thought I should use the second dataset, then got over .90 R. But I went
through some archived messages in this ML and found it wasn't a correct one
to use for regression. I used the variables imputed by the 5th imputation,
and got about .5 R, which seems right.
But I would like to see more about your thoughts of missing values (or
avoiding them) for my future survey studies --
Rich, it is great to hear you could manage limiting missing values in your
datasets... My study needs to use several common scales used in the field
(management), and my target organizations are notorious for not
participating in surveys (venture capital funds, foundations, etc.). Almost
all prior studies' response rates were about 20%. I could get over 50% of
response rate, but am still suffering with many questions not answered -- I
used paper-version, as well as online-, questionnaire by following Dillman's
recommendation So I couldn't "force" them to answer all questions.
Is there any way that I can still limit missing values?
Art, I think the reasons why participants didn't answer some questions is
because they thought the answers were "no." I mean, for instance, for the
question about whether they participate in certain network organizations,
some didn't circle the number. My assumption, by looking at the
organizations' profiles, is that they are not affiliated to such network
organizations. But, there is no way to prove all participants had the same
intention.
I used the scales used commonly in my field. The reason why I needed to use
the scales, rather than items , is because SPSS didn't allow me to run MI by
individual items since they are too many (although after I changed the level
of measurement into scale.). Also, those scales have good alphas. I left
items for some scales that don't have alphas over .70. Those decisions were
based on suggestions by prior literature such as those by Rubin, Little,
Allison, Graham, and some other empirical studies using imputed values.
Should I do anything else?
--
View this message in context:
http://spssx-discussion.1045642.n5.nabble.com/R-and-R-square-over-90-for-regression-with-imputed-dataset-tp5717033p5717054.htmlSent from the SPSSX Discussion mailing list archive at Nabble.com.
=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD
=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD