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Non-parametric inference for the effect of a treatment on survival times with application in the health and social sciences
Umeå University, Faculty of Social Sciences, Department of Statistics.
Uppsala University and IFAU, Uppsala.
2010 (English)In: Journal of Statistical Planning and Inference, ISSN 0378-3758, Vol. 140, no 7, 2122-2137 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we perform inference on the effect of a treatment on survival times in studies where the treatment assignment is not randomized and the assignment time is not known in advance. Two such studies are discussed: a heart transplant program and a study of Swedish unemployed eligible for employment subsidy. We estimate survival functions on a treated and a control group which are made comparable through matching on observed covariates. The inference is performed by conditioning on waiting time to treatment, that is, time between the entrance in the study and treatment. This can be done only when sufficient data are available. In other cases, averaging over waiting times is a possibility, although the classical interpretation of the estimated survival functions is lost unless hazards are not functions of waiting time. To show unbiasedness and to obtain an estimator of the variance, we build on the potential outcome framework, which was introduced by J. Neyman in the context of randomized experiments, and adapted to observational studies by D.B. Rubin. Our approach does not make parametric or distributional assumptions. In particular, we do not assume proportionality of the hazards compared. Small sample performance of the estimator and a derived test of no treatment effect are studied in a Monte Carlo study.

Place, publisher, year, edition, pages
Elsevier, 2010. Vol. 140, no 7, 2122-2137 p.
Keyword [en]
Employment subsidy, Heart transplant, Matching estimator, Observational study, Potential outcome, Survival function
National Category
Probability Theory and Statistics
Research subject
URN: urn:nbn:se:umu:diva-32216DOI: 10.1016/j.jspi.2010.02.012ISI: 000276369000043OAI: diva2:301988
Forte, Swedish Research Council for Health, Working Life and Welfare
Available from: 2010-03-04 Created: 2010-03-04 Last updated: 2014-03-25Bibliographically approved

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de Luna, Xavier
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