Evaluation of some random eþ ects methodology applicable to bird ringing data
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چکیده
Existing models for ring recovery and recapture data analysis treat temporal variations in annual survival probability (S ) as ® xed eþ ects. Often there is no explainable structure to the temporal variation in S1 , . . . , Sk ; random eþ ects can then be a useful model: S i 5 E(S ) + e i . Here, the temporal variation in survival probability is treated as random with average value E( e 2 ) 5 r 2 . This random eþ ects model can now be ® t in program MARK. Resultant inferences include point and inter val estimation for process variation, r 2 , estimation of E(S ) and var(Eà (S )) where the latter includes a component for r 2 as well as the traditional component for vÅ ar(Sà 1⁄2 Sà ). Furthermore, the random eþ ects model leads to shrinkage estimates, SÄ i , as improved (in mean square er ror) estimators of S i compared to the MLE, Sà i , from the unrestricted time-eþ ects model. Appropriate con ® dence intervals based on the SÄ i are also provided. In addition, AIC has been generalized to random eþ ects models. This paper presents results of a Monte Carlo evaluation of inference performance under the simple random eþ ects model. Examined by simulation, under the simple one group CormackJollySeber (CJS ) model, are issues such as bias of r à 2 , con® dence interval coverage on r 2 , coverage and mean square error comparisons for inference about S i based on shrinkage versus maximum likelihood estimators, and performance of AIC model selection over three models: S i o S (no eþ ects), S i 5 E(S ) + e i (random eþ ects), and S1 , . . . , Sk (® xed eþ ects). For the cases simulated, the random eþ ects methods performed well and were uniformly better than ® xed eþ ects
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تاریخ انتشار 2002