A Doob-Meyer decomposition under model
ambiguity: the case of compactness

Observations at a single point in time of length-at-age (LAA) for a long-lived rockfish (Sebastes alutus) show that old fish are shorter than intermediate-aged fish. Fitting of a von Bertalanffy growth model to these data produces a systematic trend in the residual of observed versus calculated LAA. We examined how such LAA data can lead to erroneous conclusions about individual growth, and whether asymptotic growth can give rise to such data. We considered two hypotheses: (i) that a time trend in growth rate resulted in larger fish in more recent years and (ii) that there are multiple growth types, where growth and mortality rates are directly related. Using a general growth model that incorporated both (i) and (ii), we show that both hypotheses can generate data identical to those for the rockfish. A single set of LAA data is inadequate for describing individual growth; however, if sufficient data are available, model ambiguity can be resolved and reasonable parameter estimates obtained. Analysis of the rockfish data indicates that (ii) is more likely to explain the observations than (i). We show how fisheries on such species may preclude our understanding these biological relationships.

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Distributionally robust optimization with multiple time scales: valuation of a thermal power plant

Computational Management Science ◽

10.1007/s10287-019-00358-0 ◽

2019 ◽

Vol 17 (3) ◽

pp. 357-385

Author(s):

Wim van Ackooij ◽

Debora Daniela Escobar ◽

Martin Glanzer ◽

Georg Ch. Pflug

Keyword(s):

Power Plant ◽

Real Option ◽

Thermal Power ◽

Model Error ◽

Multiple Time Scales ◽

Multiscale Approach ◽

Stochastic Dynamic ◽

Multiple Time ◽

Probability Models ◽

Model Ambiguity

AbstractThe valuation of a real option is preferably done with the inclusion of uncertainties in the model, since the value depends on future costs and revenues, which are not perfectly known today. The usual value of the option is defined as the maximal expected (discounted) profit one may achieve under optimal management of the operation. However, also this approach has its limitations, since quite often the models for costs and revenues are subject to model error. Under a prudent valuation, the possible model error should be incorporated into the calculation. In this paper, we consider the valuation of a power plant under ambiguity of probability models for costs and revenues. The valuation is done by stochastic dynamic programming and on top of it, we use a dynamic ambiguity model for obtaining the prudent minimax valuation. For the valuation of the power plant under model ambiguity we introduce a distance based on the Wasserstein distance. Another highlight of this paper is the multiscale approach, since decision stages are defined on a weekly basis, while the random costs and revenues appear on a much finer scale. The idea of bridging stochastic processes is used to link the weekly decision scale with the finer simulation scale. The applicability of the introduced concepts is broad and not limited to the motivating valuation problem.

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Who are You Talking About? Tracking Discourse-level Referential Processing with Event-related Brain Potentials

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2007.19.2.228 ◽

2007 ◽

Vol 19 (2) ◽

pp. 228-236 ◽

Cited By ~ 53

Author(s):

Mante S. Nieuwland ◽

Marte Otten ◽

Jos J. A. Van Berkum

Keyword(s):

Situation Model ◽

Discourse Comprehension ◽

Brain Potentials ◽

Spoken Discourse ◽

Negative Shift ◽

Model Ambiguity ◽

Referential Processing ◽

Referential Ambiguity

In this event-related brain potentials (ERPs) study, we explored the possibility to selectively track referential ambiguity during spoken discourse comprehension. Earlier ERP research has shown that referentially ambiguous nouns (e.g., “the girl” in a two-girl context) elicit a frontal, sustained negative shift relative to unambiguous control words. In the current study, we examined whether this ERP effect reflects “deep” situation model ambiguity or “superficial” textbase ambiguity. We contrasted these different interpretations by investigating whether a discourse-level semantic manipulation that prevents referential ambiguity also averts the elicitation of a referentially induced ERP effect. We compared ERPs elicited by nouns that were referentially nonambiguous but were associated with two discourse entities (e.g., “the girl” with two girls introduced in the context, but one of which has died or left the scene), with referentially ambiguous and nonambiguous control words. Although temporally referentially ambiguous nouns elicited a frontal negative shift compared to control words, the “double bound” but referentially nonambiguous nouns did not. These results suggest that it is possible to selectively track referential ambiguity with ERPs at the level that is most relevant to discourse comprehension, the situation model.

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DATA UNCERTAINTY, MODEL AMBIGUITY, AND MODEL IDENTIFICATION

Natural Resource Modeling ◽

10.1111/j.1939-7445.1987.tb00034.x ◽

1987 ◽

Vol 2 (2) ◽

pp. 159-212 ◽

Cited By ~ 18

Author(s):

Jon Schnute

Keyword(s):

Model Identification ◽

Data Uncertainty ◽

Uncertainty Model ◽

Model Ambiguity

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Implementation and impact of an extended-hours service in mental health care: lessons learned

Australian Health Review ◽

10.1071/ah15007 ◽

2015 ◽

Vol 39 (5) ◽

pp. 508 ◽

Cited By ~ 1

Author(s):

Deanna Erskine ◽

Barbara Baumgartner ◽

Sue Patterson

Keyword(s):

Mental Health ◽

Mixed Methods ◽

Mental Health Service ◽

Health Service ◽

Clinical Skills ◽

Clinical Pathways ◽

Full Description ◽

Mental Health Clinicians ◽

Model Ambiguity ◽

After Hours

Objective To describe the activity and impact of an extended-hours mental health service established to meet perceived need and improve service efficiency. Lessons developed in evaluation could usefully inform development of services in similar settings. Setting A specialist mental health service providing assessment and treatment to 330000 catchment residents of an Australian capital city. Methods Pragmatic mixed-methods evaluation, combining review of 12 months service data and interviews with 65 stakeholders; with integration of descriptive statistics and thematic analysis of qualitative data. Results Over 12 months, 2040 individuals were provided with a range of services during extended-hours, indicating that some sort of service was needed. However, evaluation demonstrated that flaws in assumptions underpinning the extended-hours service design, particularly regarding the population seeking after-hours care, necessitated adaptation of the proposed model. Ambiguity in purpose contributed to perceived lack of a cohesive identity, compounded by critical differences in the philosophies of care teams from which the extended-hours service clinicians were drawn. Nonetheless the service was considered effective by many stakeholders and co-location of different teams built collegiality within the service. Conclusions A comprehensive needs analysis, enabling full description of target populations and their needs, should underpin establishment of any service. Such understanding is needed to ensure resources are appropriate. Importantly, because mental health clinicians are not interchangeable, matching philosophy of care and clinical skills to identified need is critical to quality and efficiency. What is known about the topic? Public mental health services are obliged to deliver services which meet the needs of the service community in a timely manner. This requires enabling access to care outside routine business hours. However little is known about demand for after-hours service and literature provides little guidance to support efficient establishment of services. What does this paper add? This mixed-methods investigation of a model of extended-hours service delivery provides insights to inform development of similar services. In addition to providing detailed information about provision of services in extended hours, we evidence the specialisation of mental health clinicians who work with particular populations typically accessing care after-hours. Risk assessment and crisis management are not ‘one size fits all’ and continuity and quality of care are enhanced when philosophy of care fits consumer presentations. What are the implications for practitioners? Attention must be given to the often implicit assumptions underpinning establishment of any service. Critical to success are a thorough understanding of the problem to be addressed, clarity about and articulation of purpose and clinical pathways, and ensuring the skill mix is appropriate to need. The positive impact of co-location on collegiality will be optimised when resourcing is adequate. Further research is needed to understand the demand for after-hours service, particularly from the consumers’ perspective.

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