Hierarchical Bayes Analysis of Rare Events Using High-Dispersion Poisson Mixtures
Bibliographic record
Abstract
Modeling the occurrence of rare events such as multiyear ice or iceberg encounters, ship collisions, and several types of accidental events is often challenging because considerable dispersion is found to be associated with discrete count data. This may be due to fluctuations in the processes generating the events, or they may arise because of a complicated mixture of causal events or there may be other unexplained discontinuities. In such cases, the traditional use of the Poisson distribution is inadequate, especially when the event frequency is subsequently used to formulate design criteria based on extreme values. In this paper, the use of discrete Poisson mixtures is suggested as opposed to the simple Poisson process and continuous Poisson mixtures. One objective is to ensure that the uncertainty regarding event occurrence is well represented in both the central and tail parts of count data. The analysis of discrete Poisson mixtures involves the estimation of the number k of mixture components, the k Poisson occurrence rates, and the k weights of the mixture. Until recently such an analysis was considered daunting at best. However, the analysis can be re-cast as an equivalent Hierarchical Bayes (HB) net using an auxiliary variable vector Z of variable dimension. A Markov Chain Monte Carlo analysis can then be used to obtain the posterior distributions of the dimensionality of the mixture, the mixture weights and the occurrence rates themselves. Also, posterior distributions can be found for iceberg collision risks and iceberg scour rates. The approach is illustrated for an iceberg risk estimation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.013 | 0.039 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".