30 Dec
2012
30 Dec
'12
11:20 a.m.
Hello,
Let's say we have an ordinal variable with categories 0 to k. We take each
imputed value and subtract off the minimum ordinal value (0 in this case)
and divide by the ordinal range (k) and then restrict these transformations
to be between 0 and 1. With these probabilities, we draw a binomial random
variable for each imputed cell with k trials and probability equal to the
transformed imputation from the last sentence. Lower continuous imputed
values lead to lower probabilities and, thus, lower draws from this
binomial. Higher imputed values lead to higher draws from this binomial.
Hope that helps!
Cheers,
matt.
~~~~~~~~~~~
Matthew Blackwell
Assistant Professor of Political Science
University of Rochester
url: http://www.mattblackwell.org
On Thu, Dec 13, 2012 at 12:35 PM, audigier <audigier(a)agrocampus-ouest.fr>wrote;wrote:
Dear all,
I don't understand how amelia handles imputation of ordinal variables. We
can read in Amelia II: A Program for Missing Data:
"Imputations for variables set as ordinal are created by taking the
continuously valued imputation and using
an appropriately scaled version of this as the probability of success in a
binomial distribution. The draw from
this binomial distribution is then translated back into one of the ordinal
categories."
This is not explicit enough for me. I don't understand what does
"appropriately scaled" mean
and what's the link with binomial distribution. Can you give me more
explanations ?
Thank you for your cooperation.
V.Audigier
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