The aim of the work described in this thesis was to improve NCR's decision making process for progressing software products through the development cycle. The first chapter briefly describes the software development process at NCR, detailing documentation review and software testing techniques. The objectives and reasons for investigating software reliability models as a tool in the decision making process are outlined. There follows a short review of software reliability models, with the Littlewood and Verrall Bayesian model considered in detail. The difficulties in using this model to obtain estimates for model parameters and time to next failure are described. These estimation difficulties exist using the model on good datasets, in this case simulated failure data, and the difficulties are compounded when used with real failure data. The problems of collecting and recording failure data are outlined, highlighting the inadequacies of these collected data, and real failure data are analysed. Software reliability models are used in an attempt to quantify the reliability of real software products. The thesis concludes by summarising the problems encountered when using reliability models to measure software products and suggests future research into metrics that are required in this area of software engineering.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / M.S.

Esta dissertação apresenta a importância do gerenciamento da confiabilidade de um produto durante seu desenvolvimento. Tal gerenciamento consiste em um processo sistemático que resulta no alcance dos requisitos governamentais, do cliente e da empresa. Estudou-se a metodologia de gerenciamento da confiabilidade através do planejamento da confiabilidade meta, alocação ótima de confiabilidade, avaliação e modelagem da confiabilidade, planejamento do crescimento da confiabilidade, controle do crescimento da confiabilidade até a obtenção dos resultados planejados. Através dessa metodologia, em um estudo aplicado contemplando um produto médico-hospitalar, foi possível: (a) identificar os componentes críticos do produto, (b) identificar a lacuna existente entre o valor de confiabilidade no início do projeto quando comparado à meta, (c) planejar o crescimento da confiabilidade ao longo das fases do projeto, (d) realizar melhorias ou reprojetos nos componentes do produto, (e) controlar o crescimento da confiabilidade e (f) alcançar a confiabilidade planejada. Os resultados obtidos foram de um aumento de 24% para 100% na confiabilidade do produto para cinco anos de utilização e de 0% para 83% para dez anos de utilização. Os valores obtidos de confiabilidade superaram os valores planejados, confirmando a eficiência da metodologia adotada. / This study discusses the relevance of Product Reliability Management during the product development phase. It consists of a systematic process that results in achieving the requirements of government regulations, customer satisfaction and companies goals. We studied the Product Reliability Management methodology through five aspects, including: target planning, optimal allocation, evaluation and modeling of product reliability, growth planning, and growth control to achieve the planned results. Using this methodology, applied in a study comprising the analysis of a medical product, it was possible to: (a) identify the critical components of the product (b) identify the gap between the reliability rate at the beginning of the project when compared to the final target (c) plan the growth of reliability throughout the phases of the project (d) make improvements or redesign product components (e) control the growth of reliability and (f) achieve the planned product reliability. The obtained results show an increase of 24% to 100% on five years product reliability, and from 0% to 83% for ten years product reliability. The values of reliability exceeded the planned values, confirming the effectiveness of the Product Reliability Management methodology.

A confiabilidade do produto é um dos principais atributos da sua qualidade, porém a melhoria contínua desta confiabilidade é um objetivo inalcançável para as empresas, principalmente após o processo de globalização, no qual as empresas locais não têm como competidores apenas as empresas regionais ou nacionais, mas também as outras empresas mundiais. Outro fator importante, para o estabelecimento da confiabilidade, é o cliente que têm aumentado as suas exigências num processo contínuo, em que os aspectos de conformidade às especificações do projeto estão se tornando critério de compra. Este trabalho, através de um estudo de caso, apresenta a análise de um processo de atendimento a itens não conformes e propõe melhorias neste processo, visando agilizar a solução de problemas de campo. Para isso será avaliada a confiabilidade da empresa, desde a comunicação do cliente, passando pelo revendedor e da própria empresa, até a metodologia utilizada para a análise das falhas de campo dos produtos existentes. Os registros e informações da área de suporte e serviços, serão fundamentais para a introdução de melhorias para o procedimento atualmente em uso pela empresa. / The reliability of a product is one of the main attributes of its quality, however continuous improvement of its reliability is a never-ending journey for companies, especially those with global processes, as they must complete with other regional, national and global companies. Another important factor in determining the reliability of a product is the understanding of the critical customer requirements. Due to market globalization, consumers now have access to a greater variety of products and are better able to make comparisons between similar items. This ability drives consumers to constantly change or refine their critical requirements that ultimately influence their purchasing decisions. This case study presents an analysis of a process for monitoring product non-conformances and proposes process improvements aimed at speeding up the solution to field problems. To do this, company reliability will be analyzed in terms of the path of communication of product problems from the customer to the dealer, the dealer to the factory and from the factory to the methodology used to analyze field failures. Information from the product support and services area will be fundamental to the introduction of improvements to the current field failure processes.

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An attitude is a mental state that influences the way an individual responds to relevant objects and situations. Attitudes toward the elderly have a potential impact on all Americans, as the population is growing older. These attitudes constitute an important area of study because their nature is unclear and their impact extensive. The Kogan Attitudes Toward Old People Scale (OP) was examined to establish reliability and validity estimates. A questionnaire, consisting of this scale and four others, was administered to a sample of adults. Factor analysis of the OP revealed two factors, which were somewhat ambiguous. Internal consistency estimates for these factors and the total OP ranged from .72 to .92. Validity estimates were in the expected direction and ranged from -.13 to .36. Gender, age, education level, and degree of tolerance for others immerged as predictive variables for reported attitudes toward the elderly. It was concluded that the use of the OP is of questionable utility. If one must use it, the total OP score or only the items from Factors 1 and 2 should be utilized, as long as the discussed weaknesses, such as the sampling and validation procedures, are taken into account

The objective of this research is to develop new stochastic methods based on most probable points (MPPs) for general reliability analysis and reliability-based design optimization of complex engineering systems. The current efforts involves: (1) univariate method with simulation for reliability analysis; (2) univariate method with numerical integration for reliability analysis; (3) multi-point univariate for reliability analysis involving multiple MPPs; and (4) univariate method for design sensitivity analysis and reliability-based design optimization. Two MPP-based univariate decomposition methods were developed for component reliability analysis with highly nonlinear performance functions. Both methods involve novel function decomposition at MPP that facilitates higher-order univariate approximations of a performance function in the rotated Gaussian space. The first method entails Lagrange interpolation of univariate component functions that leads to an explicit performance function and subsequent Monte Carlo simulation. Based on linear or quadratic approximations of the univariate component function in the direction of the MPP, the second method formulates the performance function in a form amenable to an efficient reliability analysis by multiple one-dimensional integrations. Although both methods have comparable computational efficiency, the second method can be extended to derive analytical sensitivity of failure probability for design optimization. For reliability problems entailing multiple MPPs, a multi-point univariate decomposition method was also developed. In addition to the effort of identifying the MPP, the univariate methods require a small number of exact or numerical function evaluations at selected input. Numerical results indicate that the MPP-based univariate methods provide accurate and/or computationally efficient estimates of failure probability than existing methods. Finally, a new univariate decomposition method was developed for design sensitivity analysis and reliability-based design optimization subject to uncertain performance functions in constraints. The method involves a novel univariate approximation of a general multivariate function in the rotated Gaussian space; analytical sensitivity of failure probability with respect to design variables; and standard gradient-based optimization algorithms. In both reliability and sensitivity analyses, the proposed effort has been reduced to performing multiple one-dimensional integrations. Numerical results indicate that the proposed method provides accurate and computationally efficient estimates of the sensitivity of failure probability and leads to accurate design optimization of uncertain mechanical systems.

Delay discounting (the devaluation of rewards delayed in time) has been studied extensively using animal models with psychophysical adjustment procedures. Similar procedures were soon developed to assess delay discounting in humans. Although across species the same mathematical function relates discounted value to imposed delay, several methodological concerns have been implicated in human delay discounting procedures. A procedure recently developed to address these concerns is the Experiential Discounting Task (EDT). This task arranges experienced delays and rewards that humans make decisions regarding—experiencing the outcomes of their choices within session before making additional choices. The popularity of this procedure has been fueled by reports of its sensitivity to acute experimental manipulation, and that it has been predictive of treatment success. Similar sensitivity results have not been found when a traditional delay discounting task (DDT) has been used. Though the EDT appears useful for a variety of reasons, it has not been subjected to the same rigorous internal validity and reliability tests that traditional DDTs have. In two experiments we examined the test-retest reliability of the EDT (Experiment 1) and the way in which choice trials are regulated (Experiment 2). Results demonstrate that the EDT is reliable across time and choice is insensitive to trial regulation differences. We conclude with a critique of the EDT as a procedure for assessing delay discounting and hypothesize other processes it may be measuring.