Quality criteria for multimedia

The meaning of the term quality as used by multimedia workers in the field has become devalued. Almost every package is promoted by its developers as being of the ‘highest quality’. This paper draws on practical experience from a number of major projects to argue, from a quality‐assurance position, that multimedia materials should meet pre‐defined criteria relating to their objectives, content and incidence of errors

Reasoning about the Reliability of Diverse Two-Channel Systems in which One Channel is "Possibly Perfect"

This paper considers the problem of reasoning about the reliability of fault-tolerant systems with two "channels" (i.e., components) of which one, A, supports only a claim of reliability, while the other, B, by virtue of extreme simplicity and extensive analysis, supports a plausible claim of "perfection." We begin with the case where either channel can bring the system to a safe state. We show that, conditional upon knowing pA (the probability that A fails on a randomly selected demand) and pB (the probability that channel B is imperfect), a conservative bound on the probability that the system fails on a randomly selected demand is simply pA.pB. That is, there is conditional independence between the events "A fails" and "B is imperfect." The second step of the reasoning involves epistemic uncertainty about (pA, pB) and we show that under quite plausible assumptions, a conservative bound on system pfd can be constructed from point estimates for just three parameters. We discuss the feasibility of establishing credible estimates for these parameters. We extend our analysis from faults of omission to those of commission, and then combine these to yield an analysis for monitored architectures of a kind proposed for aircraft

Formal verification of a fault tolerant clock synchronization algorithm

A formal specification and mechanically assisted verification of the interactive convergence clock synchronization algorithm of Lamport and Melliar-Smith is described. Several technical flaws in the analysis given by Lamport and Melliar-Smith were discovered, even though their presentation is unusally precise and detailed. It seems that these flaws were not detected by informal peer scrutiny. The flaws are discussed and a revised presentation of the analysis is given that not only corrects the flaws but is also more precise and easier to follow. Some of the corrections to the flaws require slight modifications to the original assumptions underlying the algorithm and to the constraints on its parameters, and thus change the external specifications of the algorithm. The formal analysis of the interactive convergence clock synchronization algorithm was performed using the Enhanced Hierarchical Development Methodology (EHDM) formal specification and verification environment. This application of EHDM provides a demonstration of some of the capabilities of the system

Economic evaluations of non-communicable disease interventions

Background Demographic projections suggest a major increase in non-communicable disease (NCD) mortality over the next two decades in developing countries. In a climate of scarce resources, policy-makers need to know which interventions represent value for money. The prohibitive cost of performing multiple economic evaluations has generated interest in transferring the results of studies from one setting to another. This paper aims to bridge the gap in the current literature by critically evaluating the available published data on economic evaluations of NCD interventions in developing countries. Methods We identified and reviewed the methodological quality of 32 economic evaluations of NCD interventions in developing countries. Developing countries were defined according to the World Bank classification for low- and lower middle-income countries. We defined NCDs as the 12 categories listed in the 1993 World Bank report Investing in Health. English language literature was searched for the period January 1984 and January 2003 inclusive in Medline, Science Citation Index, HealthStar, NHS Economic Evaluation Database and Embase using medical subheading terms and free text searches. We then assessed the quality of studies according to a set of pre-defined technical criteria. Results We found that the quality of studies was poor and resource allocation decisions made by local and global policy-makers on the basis of this evidence could be misleading. Furthermore we have identified some clear gaps in the literature, particularly around injuries and strategies for tackling the consequences of the emerging tobacco epidemic. Conclusion In the face of poor evidence the role of so-called generalised cost-effectiveness analyses has an important role to play in aiding public health decision-making at the global level. Further research is needed to investigates the causes of variation among cost, effects and cost-effectiveness data within and between settings. Such analyses still need to take a broad view, present data in a transparent manner and take account of local constraints

Inequalities in purchase of mosquito nets and willingness to pay for insecticide-treated nets in Nigeria: Challenges for malaria control interventions

Objective: To explore the equity implications of insecticide-treated nets (ITN) distribution programmes that are based on user charges. Methods: A questionnaire was used to collect information on previous purchase of untreated nets and hypothetical willingness to pay (WTP) for ITNs from a random sample of householders. A second survey was conducted one month later to collect information on actual purchases of ITNs. An economic status index was used for characterizing inequity. Major findings: The lower economic status quintiles were less likely to have previously purchased untreated nets and also had a lower hypothetical and actual WTP for ITNs. Conclusion: ITN distribution programmes need to take account of the diversity in WTP for ITNs if they are to ensure equity in access to the nets. This could form part of the overall poverty reduction strategy.This study received financial support from the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical diseases

Formal verification of AI software

The application of formal verification techniques to Artificial Intelligence (AI) software, particularly expert systems, is investigated. Constraint satisfaction and model inversion are identified as two formal specification paradigms for different classes of expert systems. A formal definition of consistency is developed, and the notion of approximate semantics is introduced. Examples are given of how these ideas can be applied in both declarative and imperative forms

Measuring the effect of opportunity cost of time on participation in sports and exercise

This article has been made available through the Brunel Open Access Publishing Fund.Background: There is limited research on the association between opportunity cost of time and sports and exercise due to lack of data on opportunity cost of time. Using a sample of 14142 adults from Health Survey for England (2006), we develop and test a composite index of op-portunity cost of time (to address the current issues with data constraint on opportunity cost of time) in order to explore the relationship between opportunity cost of time and sports participation. Methods: Probit regression models are fitted adjusting for a range of covariates. Opportunity cost of time is measured with two proxy measures: a) composite index (consisting of various indicators of wage earnings) con-structed using principal component analysis; and b) education and employment, approach in the literature. We estimate the relative impact of the composite index compared with current proxy measures, on prediction of sports participation. Findings: Findings suggest that higher opportunity cost of time is associated with increased likelihood of sports participation, regardless of the time intensity of activity or the measure of opportunity cost of time used. The relative impacts of the two proxy measures are comparable. Sports and exercise was found to be positively correlated with income. Another important positive correlate of sports and exercise is participation in voluntary activity. The research and policy implications of our findings are discussed

Valuing the benefits of a health intervention using three different approaches to contingent valuation: re-treatment of mosquito bed-nets in Nigeria.

OBJECTIVES: To determine the level of willingness to pay (WTP) for re-treatment of mosquito nets and to compare the theoretical validity of WTP estimates from three contingent valuation question formats: the bidding game, binary with follow-up technique, and a novel structured haggling technique that mimicked price-taking behaviour in the study area. METHODS: WTP was elicited from randomly selected respondents from three villages in Southeast Nigeria, using pretested interviewer-administered questionnaires. Respondents' WTP for insecticide-treated nets (ITNs) was first elicited before their WTP for re-treatment of ITNs. Ordinary least-squares regression was used to assess theoretical validity. RESULTS: More than 95% of the respondents were willing to pay for re-treatment. The mean WTP was 37.1 Naira, 43.4 Naira and 49.2 Naira in the bidding game, binary with follow-up and structured haggling groups, respectively (US dollar 1.00 = 120 Naira). The WTP estimates elicited across the three question formats were statistically different (P < 0.01). Ordinary least-squares estimation showed that WTP was positively related to many variables, especially stated WTP for ITNs (P < 0.05). Structured haggling generated the highest number of statistically significant variables to explain WTP. CONCLUSIONS: The three contingent valuation approaches generated different distributions of WTP for net retreatment, possibly due to their inherent differences. Structured haggling generated the most theoretically valid estimates of WTP. The levels of WTP identified suggest that user fees exceeding 50 Naira per net re-treatment may discourage demand for the service. This is an important challenge for ITN programmes