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A parametric model for the interval censored survival times of Acacia mangium plantation in a spacing trial

Abd Kudus, K., Kimber, A. C. and Lapongan, J. (2006) A parametric model for the interval censored survival times of Acacia mangium plantation in a spacing trial. Journal of Applied Statistics, 33 (10). pp. 1067-1074. ISSN 0266-4763

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To link to this item DOI: 10.1080/02664760600746616


Survival times for the Acacia mangium plantation in the Segaliud Lokan Project, Sabah, East Malaysia were analysed based on 20 permanent sample plots (PSPs) established in 1988 as a spacing experiment. The PSPs were established following a complete randomized block design with five levels of spacing randomly assigned to units within four blocks at different sites. The survival times of trees in years are of interest. Since the inventories were only conducted annually, the actual survival time for each tree was not observed. Hence, the data set comprises censored survival times. Initial analysis of the survival of the Acacia mangium plantation suggested there is block by spacing interaction; a Weibull model gives a reasonable fit to the replicate survival times within each PSP; but a standard Weibull regression model is inappropriate because the shape parameter differs between PSPs. In this paper we investigate the form of the non-constant Weibull shape parameter. Parsimonious models for the Weibull survival times have been derived using maximum likelihood methods. The factor selection for the parameters is based on a backward elimination procedure. The models are compared using likelihood ratio statistics. The results suggest that both Weibull parameters depend on spacing and block.

Item Type:Article
Divisions:Life Sciences > School of Biological Sciences
ID Code:10122
Uncontrolled Keywords:survival times, interval censored, Weibull distribution, maximum, likelihood, backward elimination

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