An Index for Weighting Results in Catch-at-Age Models Based on Diagnostic Tests for Lack of Fit
T. Polacheck, K.A. Haskard, N. Klaer, A. Betlehem, and A. Preece
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As part of the VPA assessments of southern bluefin tuna, agreed on objective diagnostic tests designed to detect significant lack of fit are reported for each VPA analysis. However, in summarizing the current status of the stock and in the estimation of the probabilities of recovery, VPA results in which the diagnostic tests suggest significant lack of fit have been considered no differently than ones for which the test do not indicate any lack of fit. A procedure is developed whereby the results of these diagnostic tests can automatically and objectively be incorporated as an additional weight into the procedures used to combine results from different VPAs. The procedure takes into account that multiple tests are performed for a single tuning index and that possible correlation among the tests may exist. It yields a scale that accounts for both the relative lack of fit in a single index and the total number of tuning indices in which there is lack of fit. A survey was carried out using simulated assessment results to provide an indication of the performance of the procedure relative to human perceptions of what constitutes significant lack of fit. The results indicate that the two are generally consistent. The procedure is not meant as an alternative to developing and using likelihood approaches in assessments, but as an additional weighting term to be used in conjunction with both an output "likelihood" weight and an input prior weight to provide an overall relative weight when combining alternative assessment results.
- Item number: AK-SG-98-01g
- Year: 1998
- DOI: https://doi.org/10.4027/fsam.1998.07