On boundary solutions and identifiability in categorical regression with non-ignorable non-response
Clarke, PS;
(2002)
On boundary solutions and identifiability in categorical regression with non-ignorable non-response.
Biometrical journal Biometrische Zeitschrift, 44 (6).
pp. 707-17.
ISSN 0323-3847
http://www3.interscience.wiley.com/cgi-bin/abstrac...
Permanent Identifier
Use this permanent URL when citing or linking to this resource.
This paper considers the regression analysis of categorical variables when the response variable is incompletely observed and the non-response mechanism is assumed to be non-ignorable. Maximum likelihood estimation of the model parameters can lead to substantively implausible boundary solutions where the estimated proportion of non-respondents taking certain values of the response variable is zero. A geometric explanation of why boundary solutions occur was given in a previous paper for a simple model. By extending this explanation, it is possible to define the sub-class of non-ignorable models whose parameters are identified, and to show all models not in this sub-class are non-identified. The conditions under which a model is a member of this class are easily established.