Bootstrapping estimators for the seemingly unrelated regressions model

In this paper we consider the possibility of using the bootstrap to estimate the finite sample variability of feasible generalized least squares and improved estimators applied to the seemingly unrelated regressions model. The improved estimators we employ include members of the Stein-rule family and a hierarchical Bayes estimator proposed by Blattberg and George (1991). Simulation experiments are carried out using several SUR examples as well as a very large example based on the price-promotion model, and data, from marketing research.     

Exploring gaps in the online economic inclusion of persons with disabilities in Korea

ABSTRACT

This paper explores the difference in the online economic activities of people with and without disabilities in Korea. We conducted a multiple regression analysis to investigate the impact of socioeconomic characteristics, internet access, and internet skills on online economic activities. Our sample, based on a 2016 dataset that included 1554 people with disabilities and 6004 people without disabilities, was developed using quota sampling based on gender, age, and residence. We determined that individuals with disabilities were more likely to engage in online economic activities if they had higher levels of education, lived in urban areas, were employed, or had greater internet skills. Individuals without disabilities were more likely to engage in online economic activities if they were women, had higher levels of education, were employed, lived in a two-generation or more household, or had greater internet skills. For both people with and without disabilities, the level of education, employment status, and internet skills positively contribute to online economic activites. We also determined that education level, participation in economic activity, living in a two-generation or more household, and internet skills had a statistically significant influence on online economic activity for people both with and without disabilities. These results highlight the importance of education and internet training for people with disabilities, as well as social support systems that help them learn to use the internet in diverse ways through both formal and informal networks. The study also underscores the importance of information and communications technology that adequately addresses people’s needs.     

LAN property for an ergodic Ornstein–Uhlenbeck process with Poisson jumps

In this article, we consider an ergodic Ornstein–Uhlenbeck process with jumps driven by a Brownian motion and a compensated Poisson process, whose drift and diffusion coefficients as well as its jump intensity depend on unknown parameters. Considering the process discretely observed at high frequency, we derive the local asymptotic normality property. To obtain this result, Malliavin calculus and Girsanov’s theorem are applied to write the log-likelihood ratio in terms of sums of conditional expectations, for which a central limit theorem for triangular arrays can be applied.     

Analytic strategies for longitudinal networks with missing data

Missing data are often problematic when analyzing complete longitudinal social network data. We review approaches for accommodating missing data when analyzing longitudinal network data with stochastic actor-based models. One common practice is to restrict analyses to participants observed at most or all time points, to achieve model convergence. We propose and evaluate an alternative, more inclusive approach to sub-setting and analyzing longitudinal network data, using data from a school friendship network observed at four waves (N = 694). Compared to standard practices, our approach retained more information from partially observed participants, generated a more representative analytic sample, and led to less biased model estimates for this case study. The implications and potential applications for longitudinal network analysis are discussed.     

Does Iconicity in Pictographs Matter? The Influence of Iconicity and Numeracy on Information Processing,Decision Making,and Liking in an Eye‐Tracking Study

Researchers recommend the use of pictographs in medical risk communication to improve people's risk comprehension and decision making. However, it is not yet clear whether the iconicity used in pictographs to convey risk information influences individuals’ information processing and comprehension. In an eye‐tracking experiment with participants from the general population (N = 188), we examined whether specific types of pictograph icons influence the processing strategy viewers use to extract numerical information. In addition, we examined the effect of iconicity and numeracy on probability estimation, recall, and icon liking. This experiment used a 2 (iconicity: blocks vs. restroom icons) × 2 (scenario: medical vs. nonmedical) between‐subject design. Numeracy had a significant effect on information processing strategy, but we found no effect of iconicity or scenario. Results indicated that both icon types enabled high and low numerates to use their default way of processing and extracting the gist of the message from the pictorial risk communication format: high numerates counted icons, whereas low numerates used large‐area processing. There was no effect of iconicity in the probability estimation. However, people who saw restroom icons had a higher probability of correctly recalling the exact risk level. Iconicity had no effect on icon liking. Although the effects are small, our findings suggest that person‐like restroom icons in pictographs seem to have some advantages for risk communication. Specifically, in nonpersonalized prevention brochures, person‐like restroom icons may maintain reader motivation for processing the risk information.     

Accounting for Uncertainty in Heteroscedasticity in Nonlinear Regression

Toxicologists and pharmacologists often describe toxicity of a chemical using parameters of a nonlinear regression model. Thus estimation of parameters of a nonlinear regression model is an important problem. The estimates of the parameters and their uncertainty estimates depend upon the underlying error variance structure in the model. Typically, a priori the researcher would not know if the error variances are homoscedastic (i.e., constant across dose) or if they are heteroscedastic (i.e., the variance is a function of dose). Motivated by this concern, in this paper we introduce an estimation procedure based on preliminary test which selects an appropriate estimation procedure accounting for the underlying error variance structure. Since outliers and influential observations are common in toxicological data, the proposed methodology uses M-estimators. The asymptotic properties of the preliminary test estimator are investigated; in particular its asymptotic covariance matrix is derived. The performance of the proposed estimator is compared with several standard estimators using simulation studies. The proposed methodology is also illustrated using a data set obtained from the National Toxicology Program.     

A comparison of maximum likelihood and least squares for the estimation of a cumulative distribution

Monte Carlo methods are used to compare the methods of maximum likelihood and least squares to estimate a cumulative distribution function. When the probabilistic model used is correct or nearly correct, the two methods produce similar results with the MLE usually slightly superior When an incorrect model is used, or when the data is contaminated, the least squares technique often gives substantially superior results.     

An integrated model based on statistical process control and maintenance for two-stage dependent processes

The close relationship between quality and maintenance of manufacturing systems has contributed to the development of integrated models which use the concept of statistical process control (SPC) and maintenance. This article demonstrates the integration of the Shewhart individual-residual (Z_X ? Z_e) joint control chart and maintenance for two-stage dependent processes by jointly optimizing their policies to minimize the expected total costs associated with quality, maintenance and inspection. To evaluate the effectiveness of the proposed model, two stand-alone models—a maintenance model and an SPC model—are proposed. Then a numerical example is given to illustrate the application of the proposed integrated model. The results show that the integrated model outperforms the two stand-alone models with regard to the expected cost per unit time. Finally, a sensitivity analysis is conducted to develop insights into time parameters and cost parameters that influence the integration efforts.     

Inclusion of persons with disabilities in mainstream employment: is it really all about the money? A case study of four large companies in Norway and Sweden

This study investigates how large companies respond to public policy measures to ensure the inclusion of persons with disabilities in mainstream employment based on a case study of four companies in Norway and Sweden. The qualitative interviews, which were conducted with company managers, government representatives in Norway, and non-governmental organisations in Sweden, revealed three overarching themes: (1) ‘legitimacy’, (2) ‘financial interests’ and (3) ‘non-financial support’. The results indicate a more proactive response from the Swedish companies, especially regarding persons with intellectual and learning difficulties. The Norwegian companies reveal a high commitment to their own employees. These findings cannot be explained solely using neo-institutional theory, which holds that organisations demonstrate ‘conformity with powerful institutional myths to strengthen support and secure survival'. The results indicate that inclusive targeted corporate policies and programmes, advisory support, and the agency and value choices of the management might matter more.     

水平井中砂泥岩互层的双侧向测井响应研究

摘要：针对砂泥岩互层的复杂测井环境，采用三维有限元数值模拟方法，计算了多层介质模型的水平井双侧向测井响应。结果表明，井眼半径、泥浆电阻率和围岩（砂岩、泥岩）的电阻率及侵入半径与电阻率对水平井双侧向测井响应都有不同程度的影响。在砂泥岩地层中，井眼尺寸越大，泥浆电阻率越高，对视电阻率的影响越严重；当目的层厚大于8 m 后，视电阻率受围岩（砂岩、泥岩）影响很小，基本上反映地层的真实电阻率，并且曲线变化规律大致相同，此时可近似为三层介质模型；对于低阻侵入，侵入越深，视电阻率越偏离真实地层电阻率。