Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A transition model for ordinal response data with random drop-out
T2 - An application to fluvoxamine data
AU - Rezaei, Z
AU - Ganjali, M
AU - Berridge, Damon
PY - 2009/8
Y1 - 2009/8
N2 - Many methods are available to analyze incomplete longitudinal ordinal responses. In this paper a general transition model is proposed for longitudinal ordinal responses with random dropout. Maximum likelihood estimates are obtained for the transition probabilities when there are repeated observations. The likelihood function of the general model is partitioned to make possible the use of existing software to estimate model parameters. Some reduced forms of the model are also considered where for estimation of parameters in these models one has to use numerical optimization methods. The approach is applied to the well-known Fluvoxamine data. For these data, two important results, which have not been previously reported, are obtained: (1) some transition probabilities are estimated to be zero and (2) the model for current response, which conditions on previous response, removes the effects of some covariates that had previously been significant.
AB - Many methods are available to analyze incomplete longitudinal ordinal responses. In this paper a general transition model is proposed for longitudinal ordinal responses with random dropout. Maximum likelihood estimates are obtained for the transition probabilities when there are repeated observations. The likelihood function of the general model is partitioned to make possible the use of existing software to estimate model parameters. Some reduced forms of the model are also considered where for estimation of parameters in these models one has to use numerical optimization methods. The approach is applied to the well-known Fluvoxamine data. For these data, two important results, which have not been previously reported, are obtained: (1) some transition probabilities are estimated to be zero and (2) the model for current response, which conditions on previous response, removes the effects of some covariates that had previously been significant.
KW - Backward approach
KW - Cumulative logit model
KW - Gamma
KW - Longitudinal ordinal response data
KW - Partial Correlation
KW - Random dropout
UR - http://www.scopus.com/inward/record.url?scp=70449688339&partnerID=8YFLogxK
U2 - 10.1080/10543400902964100
DO - 10.1080/10543400902964100
M3 - Journal article
AN - SCOPUS:70449688339
VL - 19
SP - 658
EP - 671
JO - Journal of Biopharmaceutical Statistics
JF - Journal of Biopharmaceutical Statistics
SN - 1054-3406
IS - 4
ER -