Ian Durbach

Ian Durbach
University of Cape Town | UCT · Department of Statistical Sciences

PhD in Operational Research

About

65
Publications
15,741
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,115
Citations
Introduction
I'm interested in all aspects of decision making under uncertainty, that is, where the consequences of choices are for some reason uncertain. I also do some research in applied statistics, mostly for ecological, environmental, and energy problems.
Additional affiliations
January 2014 - present
African Institute for Mathematical Sciences South Africa
Position
  • Researcher
Description
  • Research in decision processes involving uncertainty, and applications of statistics and machine learning to ecology, environment, and energy problems
January 2012 - January 2016
University of Cape Town
Position
  • Professor (Associate)
January 2012 - present
University of Cape Town
Position
  • Senior Researcher

Publications

Publications (65)
Article
Explicitly representing uncertainty is recognised as a fundamental requirement of any long-term forecast. We propose and illustrate an expert elicitation protocol for constructing long-term probabilistic projections. Each projection represents a possible realization of a time series with autocorrelation properties, and thus a plausible future evolu...
Chapter
This chapter presents various approaches to incorporating formal modelling of risks and uncertainties into multi-criteria decision analysis, in a theoretically valid but also operationally meaningful manner. We consider both internal uncertainties (in the formulation and modelling of the decision problem), and external uncertainties arising from ex...
Article
Previous research suggests that equatorward populations of the iconic arborescent succulent Aloe dichotoma Masson are contracting in response to recent anthropogenic climate change (ACC) in southern Africa. However, previous studies did not account for small-scale spatial heterogeneity, latitudinal climatic disjunctions or when mortality occurred....
Article
The analytic hierarchy process (AHP) is a widely-used method for multicriteria decision support based on the hierarchical decomposition of objectives, evaluation of preferences through pairwise comparisons, and a subsequent aggregation into global evaluations. The current paper integrates the AHP with stochastic multicriteria acceptability analysis...
Article
his paper provides a review of multiple criteria decision analysis (MCDA) for cases where attribute evaluations are uncertain. The main aim is to identify different tools which can be used to represent uncertain evaluations, and to broadly survey the available decision models that can be used to support uncertain decision making. The review include...
Article
Full-text available
We investigate differences in perceived danger and recklessness judgements by experts (experienced skiers, N=362) and laypeople (N=2080) about participation in adventure sports across the same judgemental task using a third person perspective. We investigate the relationship between danger and recklessness and the extent to which fatality frequency...
Article
Full-text available
Progress in deep learning, more specifically in using convolutional neural networks (CNNs) for the creation of classification models, has been tremendous in recent years. Within bioacoustics research, there has been a large number of recent studies that use CNNs. Designing CNN architectures from scratch is non-trivial and requires knowledge of mach...
Article
Full-text available
Aim Snow leopards are distributed across the mountains of 12 countries spread across 1.8 million km² in Central and South Asia. Previous efforts to map snow leopard distributions have relied on expert opinions and modelling of presence-only data. Expert opinion is subjective and its reliability is difficult to assess, while analyses of presence-onl...
Article
Full-text available
Extracting species calls from passive acoustic recordings is a common preliminary step to ecological analysis. For many species, particularly those occupying noisy, acoustically variable habitats, the call extraction process continues to be largely manual, a time‐consuming and increasingly unsustainable process. Deep neural networks have been shown...
Article
Full-text available
Video data are widely collected in ecological studies, but manual annotation is a challenging and time‐consuming task, and has become a bottleneck for scientific research. Classification models based on convolutional neural networks (CNNs) have proved successful in annotating images, but few applications have extended these to video classification....
Article
1. Spatial capture-recapture (SCR) methods use the location of detectors (camera traps, hair snares, live-capture traps) and the locations at which animals were detected (their spatial capture histories) to estimate animal density. Despite the often large expense and effort involved in placing detectors in a landscape, there has been relatively lit...
Preprint
Full-text available
Extracting species calls from passive acoustic recordings is a common preliminary step to ecological analysis. For many species, particularly those occupying noisy, acoustically variable habitats, the call extraction process continues to be largely manual, a time-consuming and increasingly unsustainable process. Deep neural networks have been shown...
Article
We consider portfolio decision problems with positive interactions between projects. Exact solutions to this problem require that all interactions are assessed, requiring time, expertise and effort that may not always be available. We develop and test a number of fast and frugal heuristics – psychologically plausible models that limit the number of...
Article
Rugby union, like many sports, is based around sequences of play, yet this sequential nature is often overlooked, for example in analyses that aggregate performance measures over a fixed time interval. We use recent developments in convolutional and recurrent neural networks to predict the outcomes of sequences of play, based on the ordered sequenc...
Article
Many animals increase the intensity of their vocalizations in increased noise. This response is known as the Lombard effect. While some previous studies about cetaceans report a 1 dB increase in the source level (SL) for every dB increase in the background noise level (NL), more recent data have not supported this compensation ability. The purpose...
Article
• Variation in plant breeding systems has implications for pollinator‐mediated selection on floral traits and the ecology of populations. Here we evaluate pollinator contribution to seed production, self‐compatibility and pollen limitation in different colour forms of Drosera cistiflora sensu lato (Droseraceae). These insectivorous perennial plants...
Preprint
Full-text available
Video data are widely collected in ecological studies but manual annotation is a challenging and time-consuming task, and has become a bottleneck for scientific research. Classification models based on convolutional neural networks (CNNs) have proved successful in annotating images, but few applications have extended these to video classification....
Method
Full-text available
PAWS aims to produce a robust estimate of the snow leopard’s population status
Article
Minke whales were acoustically detected, localized, and tracked on the U.S. Navy's Pacific Missile Range Facility from 2012 to 2017. Animal source levels (SLs) were estimated by adding transmission loss estimates to measured received levels of 42 159 individual minke whale boings. Minke whales off Hawaii exhibited the Lombard effect in that they in...
Chapter
This chapter presents behavioral issues arising from various approaches for including risk and uncertainty in multi-criteria decision analysis (MCDA). The chapter is a behaviorally oriented reassessment and reinterpretation of our earlier reviews on uncertainty modeling in MCDA, updated to include recent developments. We review the limitations of p...
Article
Every day national power system networks provide thousands of MW of electric power from generating units to consumers, requiring different operations and planning to ensure secure systems. Where demand exceeds supply, load shedding - controlled, enforced reduction in supply - is necessary to prevent system collapse. Should load shedding need to be...
Article
Full-text available
The notion of risk plays a central role in economics, finance, health, psychology, law and elsewhere, and is prevalent in managing challenges and resources in day‐to‐day life. In recent work, Duncan Pritchard (2015, 2016) has argued against the orthodox probabilistic conception of risk on which the risk of a hypothetical scenario is determined by h...
Article
Multicriteria decision analysis and scenario planning are complementary tools for supporting large‐scale, strategic decision making, but there has been limited interaction between the fields. This paper describes how scenario planning can be integrated with the analytic hierarchy process (AHP), one of the most popular approaches in decision analysi...
Article
This paper presents empirical evidence of historical vegetation and climate change in the arid Pro-Namib and hyper-arid Namib Desert spanning the late 19th century to the present based on one hundred archival landscape photographs that have been re-photographed or ‘matched’. Each photo site was evaluated for changes in woody cover and taken togethe...
Article
Full-text available
Background Understanding white shark (Carcharodon carcharias) habitat use in coastal areas adjacent to large cities, is an important step when formulating potential solutions to the conservation conflict that exists between humans and large predatory sharks. In this study, we present the findings of a 2.5-year study of white shark occurrence and mo...
Article
The ever-increasing availability of large data-sets that store users’ judgements (such as forecasts and preferences) and choices (such as acquisitions of goods and services) provides a fertile ground for Behavioural Operational Research (BOR). In this paper, we review the streams of Behavioural Decision Research that might be useful for BOR researc...
Article
Full-text available
In this paper, we present the results of two surveys that investigate subjects’ judgments about what can be known or justifiably believed about lottery outcomes on the basis of statistical evidence, testimonial evidence, and “mixed” evidence, while considering possible anchoring and priming effects. We discuss these results in light of seven distin...
Article
Many decisions can be analyzed and supported by quantitative models. These models tend to be complex psychologically in that they require the elicitation and combination of quantities such as probabilities, utilities, and weights. They may be simplified so that they become more transparent, and lead to increased trust, reflection, and insight. Thes...
Article
We conduct a validation study to determine which historically statistically significant rugby union team key performance indicators (KPIs) continue to be valid differentiators between winning and losing teams. We examine KPI validity within and among five competitions across 2013, 2014 and 2015 by determining which KPIs continue to achieve statisti...
Article
The occurrence of unexpected events that are extreme in magnitude, rare in frequency, and short-lived in duration poses distinctive challenges to decision makers and planners. In this paper we examine the impact of negative versions of these events, which we term “shocks”, on the judgmental forecasts of subjects experiencing them. A behavioral expe...
Article
Full-text available
Several experimental and animal studies have demonstrated that substances rich in antioxidants can reduce the physicochemical and peroxidative risk factors for calcium oxalate (CaOx) renal stone formation in urine and blood. However, there are very few such investigations in humans. In the present pilot study, two varieties of tea, a green one from...
Article
Full-text available
It has often been observed that changing an item's position in a list can substantially affect the probability that it is chosen. This paper assesses the magnitude of these so-called order effects in brand-attribute association tasks, and examines the confounding roles played by brand usage and question framing. While our main order effect is rough...
Article
Full-text available
Many professional rugby teams collect extensive data on player performance, but the synthesis of this data into overall evaluations and subsequent selections is still largely left to the expert but unassisted judgment of coaching staff. Decision support systems are designed to assist this process by providing a framework for making decisions in a s...
Article
Full-text available
Many professional rugby teams collect extensive data on player performance, but the synthesis of this data into overall evaluations and subsequent selections is still largely left to the expert but unassisted judgment of coaching staff. Decision support systems are designed to assist this process by providing a framework for making decisions in a s...
Article
Full-text available
Windthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance r...
Article
This paper considers the use of scenarios to treat uncertain attribute evaluations in the outranking methods. The scenario-based approach allows the decision maker to think deterministically about the problem by attaching causal links to a small number of potential outcomes, instead of using probability distributions. The scenario approach can be e...
Article
Full-text available
A sequence of purchases may undergo sudden changes at unknown times. In this paper we assess the extent of such change by developing a multiple change-point model that assumes that there is an underlying sequence of choice probabilities that govern the observed sequence of purchases, and that this sequence of probabilities can be partitioned into c...
Article
Background Supersaturation (SS) of urinary salts has been extensively invoked for assessing the risk of renal stone formation, but precursors have often been ignored. Our objectives were to establish by computer modeling, which urinary components are essential for calculating reliable SS values, to investigate whether unique equilibrium processes o...
Article
Full-text available
This paper conducts a search for community structure in the South African company network, a social network whose elements are South African companies listed on the Johannesburg Stock Exchange. Companies are connected in this network if they share one or more directors on their respective boards. Discovered clusters, called communities, can be cons...
Article
Full-text available
In limited overs cricket, efficiency plays a significant role in team success. Batsmen especially are under pressure to score quickly rather than in large quantities because only 50 overs are available per innings. This paper uses data envelopment analysis (DEA) and stochastic multicriteria acceptability analysis (SMAA) to assess the efficiency wit...
Article
Full-text available
Dedication to Emeritus Professor Theodor Stewart To Theo, for his enormous, enduring (and continuing!) contribution to the theory and practice of operational research at the University of Cape Town. Abstract This paper explores the theme of training operational research (OR) practitioners in South Africa by critically evaluating a Masters program i...
Article
Full-text available
This paper describes an application providing decision support for generating a shortlist of promising electricity-saving options for households in South Africa. The decision problem is characterised by constraints on time and other resources, and by substantial uncertainty around the preferences for energy-related attributes and the performance of...
Article
This paper reports results from two empirical tests of the descriptive validity of synthesis axioms used by the evidential reasoning (ER) approach to aggregate performance over multiple criteria. These show that evaluations which invoke the axioms frequently violate them. The two most systematic aspects of the violations are that aggregate evaluati...
Article
Uncertainty is present in many decisions where an action's consequences are unknown because they depend on future events. Multi-attribute utility theory (MAUT) offers an axiomatic basis for choice, but practitioners may prefer to use simpler decision models for transparency, ease of use, or other practical reasons. We identify some ‘simplified’...
Article
This paper provides a review of multiple criteria decision analysis (MCDA) for cases where attribute evaluations are uncertain. The main aim is to identify different tools which can be used to represent uncertain evaluations, and to broadly survey the available decision models that can be used to support uncertain decision making. The review includ...
Article
This paper presents the results of an experiment investigating the effects of using different formats for representing uncertain attribute evaluations on decision making. Study participants make a series of hypothetical choices using six uncertainty formats – probability distributions, expected values, standard deviations, three-point (minimum–medi...
Article
Full-text available
An application of building a system dynamics model of the way households might respond to interventions aimed at reducing energy consumption (specifically the use of electricity) is described in this paper. A literature review of past research is used to build an initial integrated model of household consumption, and this model is used to generate...
Article
This paper proposes and evaluates a descriptive multiattribute choice model based upon the notion of acceptability developed in the stochastic multicriteria acceptability analysis (SMAA) methods. The acceptability index is simply the relative proportion of all possible preference structures that support the selection of a particular alternative, an...
Article
This paper addresses the task of estimating the kind of aspirations that are most likely to have given rise to an observed partial rank ordering of alternatives. The proposed approach uses a Tchebycheff goal programming formulation to serve as a descriptive model of choice and stochastic multicriteria acceptability analysis to generate candidate as...
Article
Full-text available
In this paper we analyse the networks created from directors sitting on the boards of companies in South Africa. We consider two projections of this network: a director network, in which only directors are present and two directors are linked if they sit together on one or more common boards; and a firm network, in which only firms are present and...
Article
Full-text available
A simulation study examines the impact of a simplification strategy that replaces distributional attribute evaluations with their expected values and uses those expectations in an additive value model. Several alternate simplified forms and approximation approaches are investigated, with results showing that in general the simplified models are abl...
Article
Full-text available
Behavioural research into slot machine gambling tends to focus on characteristics of the gambler or on qualitative aspects of the slot machine such as audiovisual displays and bonus features. In this paper we take a different approach by using Monte Carlo simulation to relate hypothetical slot machine gambling behaviour to the statistical character...
Article
Full-text available
Co-authorship networks are graphs in which the nodes of the graph represent authors and two authors are connected by an edge if they have written one or more papers together. When applied to the authorship of scholarly papers, analysing the structure of a co-authorship network can provide useful insights into the way in which research is carried ou...
Article
This article illustrates the concept of statistical independence using the example of slot machines that may be played on multiple lines.
Conference Paper
Full-text available
We investigate a framework where agents search for satis- fying products by using referrals from other agents. Our model of a mechanism for transmitting word-of-mouth and the resulting behavioural effects is based on integrating a module governing the local behaviour of agents with a mod- ule governing the structure and function of the underlying n...
Article
Full-text available
This paper considers a commonly-held belief about sequential cricketing data, which states that batsmen go through periods of good and bad batting 'form' that are longer than one could expect from the outcome of a random process. We test this belief against empirical data, find a distinct lack of support for it, and give some simple psychological e...
Conference Paper
Full-text available
We use an agent-based model to examine the influence of word-o f-mouth communication in environments where agents select products by using positive referrals from oth er satisfied agents as well as their own preferences and perce ptions. The role of referrals is illustrated using a complex decision environment that incorporates a number of psycholo...
Article
Stochastic multicriteria acceptability analysis using achievement functions (SMAA- A) is a preference model for discrete-choice decision making that inverts the tra- ditional goal programming process by asking what combinations of aspirations are necessary to make each alternative the preferred one, rather than what alternative is preferred given a...
Article
This paper concerns the integration of goal programming and scenario planning as an aid to decision making under uncertainty. Goal programming as a methodology emphasises the resolution of conflict among criteria; scenario planning focuses on the treatment of uncertainty relating to future states of the world. Integrating the two methodologies is b...

Network

Cited By

Projects

Project (1)