A Theoretical Foundation for the Development of Process Capability Indices and Process Parameters Optimization under Truncated and Censoring Schemes

Process capability indices (PCIs) provide a measure of the output of an in-control process that conforms to a set of specification limits. These measures, which assume that process output is approximately normally distributed, are intended for measuring process capability for manufacturing systems. After implementing inspections, however, non-conforming products are typically scrapped when units fail to meet the specification limits; hence, after inspections, the actual resulting distribution of shipped products that customers perceive is truncated. In this research, a set of customer-perceived PCIs is developed focused on the truncated normal distribution, as an extension of traditional manufacturer-based indices. Comparative studies and numerical examples reveal considerable differences among the traditional PCIs and the proposed PCIs. The comparison results suggest using the proposed PCIs for capability analyses when non-conforming products are scrapped prior to shipping to customers. The confidence interval approximations for the proposed PCIs are also developed. A simulation technique is implemented to compare the proposed PCIs with its traditional counterparts across multiple performance scenarios. The robust parameter design (RPD), as a systematic method for determining the optimum operating conditions that achieve the quality improvement goals, is also studied within the realm of censored data. Data censoring occurs in time-oriented observations when some data is unmeasurable outside a predetermined study period. The underlying conceptual basis of the current RPD studies is the random sampling from a normal distribution, assuming that all the data points are uncensored. However, censoring schemes are widely implemented in lifetime testing, survival analysis, and reliability studies. As such, this study develops the detailed guidelines for a new RPD method with the consideration of type I-right censoring concepts. The response functions are developed using nonparametric methods, including the Kaplan-Meier estimator, Greenwood\u27s formula, and the Cox proportional hazards regression method. Various response-surface-based robust parameter design optimization models are proposed and are demonstrated through a numerical example. Further, the process capability index for type I-right censored data using the nonparametric methods is also developed for assessing the performance of a product based on its lifetime

Improving the Use of Experimental Auctions in Africa: Theory and Evidence

Experimental auctions have not been widely used in Africa. However, auctions are important tools for evaluating new products and technologies. To increase the quality of these experiments, we explore an alternative first-price bidding mechanism that is more similar to African market exchanges and we analyze factors likely to affect bidding. Experiments with African consumers show that the proposed first-price mechanism has no advantage over conventional second-price mechanisms. Results show high and significant cash-in-hand, experimenter, and time of day effects in main rounds, and significant ordering effects in test rounds. These effects need to be carefully considered when applying the Becker-DeGroot-Marschak mechanism in Africa.Africa, BDM mechanism, experimenter effect, first-price auction, income effect, order effect, time of day effect, Research Methods/ Statistical Methods,

DEVELOPMENT OF THE INTEGRATED CENSORED ROBUST-TOLERANCE ENGINEERING DESIGN SYSTEMS VIA IMPROVED RESPONSE SURFACE MODELING

In this dissertation, we intend to integrate censoring into robust-tolerance engineering using improved dual response surface modeling. This is perhaps the first attempt in the quality control literature. In the literature, response surface models have largely been restricted to second order (or quadratic) models and robust-tolerance designs have been restricted to situations involving complete observations. We intend to show that higher order response surface models can be more powerful in terms of prediction ability, and are therefore more reliable than the preferred quadratic models in the general context of robust design. We will also consider formulating robust and tolerance designs in the presence of censored data. This is especially important for lifetime studies, where experiments are designed to determine the expected lifetimes of products under a variety of conditions. It is most often necessary to terminate experiments of this nature before the failure of the all the elements in the sample. Thus, lifetimes are observed for failed items, but censored times are observed for surviving items only. Available robust design methodologies in the literature have paid very little or no attention to problems of this nature. The proposed study is naturally suited for larger-the-better type (L-type) quality characteristics. As a result to this, we intend to propose quality loss functions that properly model such quality characteristics in a very intuitive and practical way. At the conclusion of the study, we intend to develop a censored-robust tolerance design optimization procedure, which will integrate all the major concepts of this dissertation

E-business and Export Behaviour: Evidence from Indian Firms

E-business, international orientation, India

Impacts of inventory credit, input supply shops, and fertilizer microdosing in the drylands of Niger:

"This study investigated the impacts of access to inventory credit, input supply shops, fertilizer microdosing demonstrations, and other factors on farmers' use of inorganic fertilizer and other inputs in Niger and on crop yields. We found that access to inventory credit and input supply shops has increased the use of inorganic fertilizer and seeds and that microdosing demonstrations have increased the use of inorganic fertilizer. Ownership of traction animals and access to off-farm employment have also contributed to the use of inorganic fertilizer, while larger farms use less fertilizer and labor per hectare. The impacts of these interventions and technologies depend on the crop mix. Inorganic fertilizer has a positive impact on millet and millet–cowpea yields when applied using microdosing, with an estimated marginal value-cost ratio greater than 3 for those crops indicating significant profitability. By contrast, microdosing has a negative impact on yields of the millet–sorghum–cowpea intercrop, suggesting that microdosing should not be promoted when sorghum is part of the crop mix. However, better access to input supply shops has contributed to higher yields of the millet–sorghum–cowpea intercrop. The predicted effect of inventory credit on farmers' income as a result of increased inorganic fertilizer use is an increase of 5,000 to 10,000 FCFA per hectare (about US$10 to US$20 per hectare in 2005) in millet or millet–cowpea production. Similarly, being 10 km closer to an input supply shop is predicted to increase farmers' income by 3,200 to 4,500 FCFA per hectare. These benefits do not take into account the impacts of the interventions on seeds or other inputs, which are also generally positive. The positive impacts are linked to the use of fertilizer microdosing, which has increased the productivity of fertilizer use in millet and millet–cowpea production, indicating synergies among the various interventions. They are also linked to these specific crops, because we found less favorable impacts of these interventions for the millet–sorghum–cowpea intercrop and for peanuts. Other interventions that could help to boost the use of inputs and productivity include promotion of improved access to farm equipment and traction animals and promotion of higher-value crops such as hibiscus. Further research on these topics appears warranted. Research on the implications of interventions on land degradation would also be useful." from Author's AbstractFertilizer microdosing, Inventory credit, Warrantage, Input supply shops, Drylands, Land management,

Exchange Rate Pass-Through in ASEAN: Identifying Supply-Side Constraints to Export Performance in Ecuador: An Exercise with Investment Climate Survey Data

We apply a Heckman selection model to the 2003-Investment Climate Survey (ICS) to investigate supply-side constraints to export performance at the firm level in Ecuador. To correct for the non-random truncation problem, we use the Heckman selection model to estimate the probability of exporting (export propensity) and the share of total sales that are exported (export intensity) by Ecuadorian firms. A baseline model with 12 independent variables divided into three categories – idiosyncratic characteristics, technology, and business environment – is developed. Three other models are developed with the addition of variables related to trade integration, business environment, and infrastructure. Results corroborate with the hypothesis implicit in the Heckman model, which considers both decisions made by a firm – whether to export, and how much of its sales to export – to be interdependent. In the Ecuadorian case, three important results for the firm’s export performance are found: technology matters; infrastructure does not; and trade orientation is significant, with specialized firms tending to have smaller export intensity when having the countries of the Andean Community as their main trade partners, the opposite happening if the U.S. is their main trade partner. We find a robust and stable relationship for export propensity and intensity with size, import of inputs, labor regulations, in-house R&D, quality certification, web-use, and foreign ownership. Also, capacity utilization and trade with the U.S. positively affect export intensity, while trade within the Andean Community has the opposite effect in our outcome variable. No significant relationship was found for the infrastructure variables.World Bank Policy Research Working Paper 4179, March 2007.Ecuador; exports; innovation; foreign networks; business environment; firm level

Identifying supply-side constraints to export performance in Ecuador : an exercise with Investment Climate Survey data

The authors apply a Heckman selection model to the 2003 Investment Climate Survey (ICS) to investigate supply-side constraints to export performance at the firm level in Ecuador. To correct for the non-random truncation problems, they use the Heckman selection model to estimate the probability of exporting (export propensity) and the share of total sales that are exported (export intensity) by Ecuadorian firms. They develop a baseline model with 12 independent variables divided into three categories-idiosyncratic characteristics, technology, and business environment. The authors develop three other models with the addition of variables related to trade integration, business environment, and infrastructure. Results corroborate with the hypothesis implicit in the Heckman model, which considers both decisions made by a firm-whether to export, and how much of its sales to export-to be interdependent. In the Ecuadorian case, they find three important results for the firm's export performance: technology matters; infrastructure does not; and trade orientation is significant, with specialized firms tending to have smaller export intensity when their main trade partners are countries of the Andean Community, and the opposite happening if the United States is their main trade partner. The authors find a robust and stable relationship for export propensity and intensity with size, import of inputs, labor regulations, in-house research and development, quality certification, web-use, and foreign ownership. Also, capacity utilization and trade with the United States positively affect export intensity, while trade within the Andean Community has the opposite effect in the outcome variable. But they find no significant relationship for the infrastructure variables.Free Trade,Private Participation in Infrastructure,Microfinance,Small Scale Enterprise,Markets and Market Access

The role of inter-organizational collaboration within innovation strategies: towards a portfolio approach.

Within the innovation literature, inter-organizational collaboration is being advanced as instrumental for improving the innovative performance of firms. In addition inter-organizational collaboration can be instrumental for addressing the multiple requirements innovation strategies entail. At the same time - large scale - empirical evidence for such a relation is scarce. Within this paper we examine whether evidence can be found for the idea that inter-organizational collaboration supports the effectiveness of innovation strategies. Multivariate and Tobit analyses of data on Belgian manufacturing firms, collected by means of the CIS survey (n=221), reveals a positive relationship between inter-organizational collaboration and innovative performance. Moreover the findings reported here suggest the relevancy of adopting a portfolio approach towards inter-organizational collaboration.Data; Effectiveness; Firms; Innovation; Innovation strategy; Manufacturing; Performance; Portfolio; Requirements; Strategy; Time;

Reward crowdfunding campaigns: Time-to-success analysis

The time-to-success of reward crowdfunding campaigns constitutes a relevant topic that has been neglected in business literature. In this study, we employ parametric and semi-parametric models of survival analysis to identify the determining factors of the duration of success of these campaigns. Based on more than 4,200 reward crowdfunding campaigns, our results are robust for controls and reveal that the campaigns that attain success most rapidly are located predominantly in cities with greater income inequality. These are cities that are characterized by lower fundraising targets and receive a larger number of pledges. In addition, our covariates indicate a non-constant influence on time-to-success during the fundraising period.Fundação para a Ciência e Tecnologia (FCT

DETERMINANTS OF FOOD INDUSTRY PERFORMANCE – SURVEY DATA AND REGRESSIONS FOR DENMARK

This paper investigates empirically the determinants of firms’ performance in the agrifood sector by using recent survey data for Denmark. Treating sales per employee as a proxy for value added we estimate several bootstrapped regression models to draw conclusions on the marginal effects of potential performance determinants such as the form and nature of ownership, stage of the food chain and commodity sector, new product development, staff quality, firms’ competitive stance, and elements of firms’ strategy. To draw robust inferences we apply, besides the ordinary heteroscedasticity corrected Tobit ML-estimator, a nonparametric least absolute deviations estimator (LAD/CLAD) based on a quantile regression procedure. The results indicate that we cannot reject the hypothesis of no influence of dominant orientation on value added. Rather, firms’ focus on human capital, stage and commodity sector better explains their value addition. We reject the hypothesis that regional networks have no influence on value added. Location in Århus, emphasis on human capital and the negative influence of outsourcing on value added all provide supporting evidence. We reject the hypothesis of no influence of FDI, and moreover propose that FDI has targeted the domestic Danish market as a source of value added.value added, innovation, organizational type, Food Consumption/Nutrition/Food Safety, Q13, O31, O33,