Missing covariate data in parametric survival analysis : modelling the missing data mechanism
Boyd, K. L. and Hutton, Jane (Statistician) (2006) Missing covariate data in parametric survival analysis : modelling the missing data mechanism. Working Paper. Coventry: University of Warwick. Centre for Research in Statistical Methodology. Working papers, Vol.2006 (No.2).
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Official URL: http://www2.warwick.ac.uk/fac/sci/statistics/crism...
Aims and Motivation To examine the effect of level of disability on the survival
of children with cerebral palsy using a cohort taken from Bristol. The data
is subject to, possibly not missing at random (NMAR), unobserved covariate
Methods A joint survival model for the log-survival times and missing data mechanism is introduced. This approach enables us to model the missing data
mechanism. This is then used to model the effect of level of ambulatory disability on survival in the cerebral palsy data. Extensions to the model are
discussed to include continuous and multiple covariates.
Results Analysis suggests that the effect of severe ambulation on survival in individuals with cerebral palsy is underestimated if no account is taken of the
missing data mechanism. Simulations show that this model, under various
distribution assumptions, performs well in comparison to basic exclusion techniques.
Conclusions It is very important to consider the mechanism behind any missing
data when studying survival. Slight deviances from the less restrictive assumptions can effect parameter estimates in survival models. In our data, we see an
increased effect of severe ambulation on survival in those with cerebral palsy.
A severe level of ambulatory disability causes a decrease in survival.
|Item Type:||Working or Discussion Paper (Working Paper)|
|Subjects:||Q Science > QA Mathematics|
|Divisions:||Faculty of Science > Statistics|
|Library of Congress Subject Headings (LCSH):||Missing observations (Statistics), Survival analysis (Biometry), Cerebral palsy -- Mathematical models|
|Series Name:||Working papers|
|Publisher:||University of Warwick. Centre for Research in Statistical Methodology|
|Place of Publication:||Coventry|
|Number of Pages:||25|
|Status:||Not Peer Reviewed|
|Access rights to Published version:||Open Access|
Collett, D. (1999), Modelling Survival Data in Medical Research, Chapman & Hall /
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