[Forum SIS] Seminario M. Giovanna Ranalli

[Paola Vicard]

************** AVVISO DI SEMINARIO***************

Mercoledì 8 febbraio 2012 alle ore 15,00
presso l'Aula 20 del Dipartimento di Economia,
Università Roma Tre, Via Silvio D’Amico 77

Maria Giovanna Ranalli
Università degli Studi di Perugia

terrà un seminario dal titolo:

ADJUSTING FOR NONIGNORABLE NONRESPONSE USING A LATENT VARIABLE MODELING 
APPROACH

Abstract:
Nonresponse is present in almost all surveys and can severely bias 
estimates. It is usually distinguished between unit and item 
nonresponse: in the former, we completely fail to have information from 
a unit selected in the sample, while in the latter, we observe only part 
of the information on the selected unit. Unit nonresponse is usually 
dealt with by reweighting: each unit selected in the sample has 
associated a sampling weight and an unknown response probability; the 
initial sampling weight is multiplied by the inverse of estimated 
response probabilities. Item nonresponse is usually dealt with by 
imputation. By noting that for a particular survey variable, we just 
have observed and unobserved values, in this work we exploit the 
connection between unit and item nonresponse. In particular, we assume 
that the factors that drive unit response are the same as those that 
drive item response on selected variables of interest. Response 
probabilities are then estimated by using a logistic regression with a 
latent covariate that measures such "will to respond" and that can 
explain part of the unknown behaviour of a unit to participate in the 
survey. The latent covariate is estimated using latent trait models. 
Such approach is particularly relevant for sensitive items and, 
therefore, can handle non-ignorable nonresponse. Auxiliary information 
known for both respondents and nonrespondents can be included either in 
the latent variable model or in the logistic model. The approach can be 
also used when auxiliary information is not available, and we analyze 
here this case. The theoretical properties of the proposed estimators 
are sketched and simulations studies are conducted to illustrate their 
finite size sample performance.


Tutti gli interessati sono invitati a partecipare.


-- 
Paola Vicard
Dipartimento di Economia
Università Roma Tre
Via Silvio D'Amico 77
00145 Roma, Italia
Tel: +39 06 57335684
Fax: +39 06 57335771
E-mail: vicard a uniroma3.it
Personal web page: http://tinyurl.com/29tnjw5
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