Estimation of δ=P(X<Y) for Burr XII distribution based on the progressively first failure-censored samples

Let X and Y have two-parameter Burr XII distributions. The maximum-likelihood estimator of δ=P(X<Y) is studied under the progressively first failure-censored samples. Three confidence intervals of δ are constructed by using an asymptotic distribution of the maximum-likelihood estimator of δ and two bootstrapping procedures, respectively. Some computational results from intensive simulations are presented. An illustrative example is provided to demonstrate the application of the proposed method.     

Mis-specification analyses of gamma and Wiener degradation processes

Degradation models are widely used these days to assess the lifetime information of highly reliable products if there exist some quality characteristics (QC) whose degradation over time can be related to the reliability of the product. In this study, motivated by a laser data, we investigate the mis-specification effect on the prediction of product's MTTF (mean-time-to-failure) when the degradation model is wrongly fitted. More specifically, we derive an expression for the asymptotic distribution of quasi-MLE (QMLE) of the product's MTTF when the true model comes from gamma degradation process, but is wrongly assumed to be Wiener degradation process. The penalty for the model mis-specification can then be addressed sequentially. The result demonstrates that the effect on the accuracy of the product's MTTF prediction strongly depends on the ratio of critical value to the scale parameter of the gamma degradation process. The effects on the precision of the product's MTTF prediction are observed to be serious when the shape and scale parameters of the gamma degradation process are large. We then carry out a simulation study to evaluate the penalty of the model mis-specification, using which we show that the simulation results are quite close to the theoretical ones even when the sample size and termination time are not large. For the reverse mis-specification problem, i.e., when the true degradation is a Wiener process, but is wrongly assumed to be a gamma degradation process, we carry out a Monte Carlo simulation study to examine the effect of the corresponding model mis-specification. The obtained results reveal that the effect of this model mis-specification is negligible.     

An error-bounded polynomial approximation for bivariate normal probabilities

Although the bivariate normal distribution is frequently employed in the development of screening models, the formulae for computing bivariate normal probabilities are quite complicated. A simple and accurate error-bounded, noniterative approximation for bivariate normal probabilities based on a simple univariate normal quadratic or cubic approximation is developed for use in screening applications. The approximation, which is most accurate for large absolute correlation coefficients, is especially suitable for screening applications (e.g., in quality control), where large absolute correlations between performance and screening variables are desired. A special approximation for conditional bivariate normal probabilities is also provided which in quality control screening applications improves the accuracy of estimating the average outgoing product quality. Some anomalies in computing conditional bivariate normal probabilities using BNRDF and NORDF in IMSL are also discussed.     

Properties and performance of one-sided cumulative count of conforming chart with parameter estimation in high-quality processes

The one-sided cumulative count of conforming (CCC) chart is a useful method to monitor nonconforming fraction in high-quality manufacturing processes. The nonconforming fraction parameter is assumed to be known when implementing a one-sided CCC chart. In this study, we investigated the impact of estimated nonconforming fraction, [pcirc] ₀, in a one-sided CCC chart. The run length distribution is derived as well as the conditional probability of a false alarm rate (CFAR), conditional average run length (CARL) and its standard deviation (CSDRL). Simulation results are conducted to evaluate the effect of [pcirc] ₀ in a one-sided CCC chart. The results show that values of CFAR, CARL and CSDRL are close to the nominal values for a large sample. The impact of estimation errors was also studied. We find that CFAR decreases for large [pcirc] ₀. Thus, a large value of [pcirc] ₀ is suggested for fewer false alarms.     

The Minimal Spanning Tree Preservation Approaches for DNA Multiple Sequence Alignment and Evolutionary Tree Construction

In this paper, we propose a new criterion, namely the minimal spanning tree preservation approach, for both of the DNA multiple sequence alignment and the construction of evolutionary trees. It is our aim to keep the proximity information among the sequences or species via our approach. The basic idea behind this approach is that those distances among species which are close to one another are more informative than the others.     

An Exploratory Study of “Parasites” in Taiwan

Deriving from Parasite Single proposed by Yamada (1997), parasites in this study is redefined as those who live with and financially rely on their parents in terms of living expenses after school graduation. The current study adopts the logit model and utilizes the data from the 1999 to 2000 Taiwan Panel Study of Family Dynamics to investigate the determinants of parasites. The finding reveals that gender, age, marital status, and the value of filial piety are significantly different between parasites and non-parasites. Moreover, gender, monthly income, age and marital status are determinants of the probability of being parasites.     

The Effects of Cultural Familiarity and Question Preview Type on the Listening Comprehension of L2 Learners at the Secondary Level

We examined the effect of cultural familiarity and question-preview types on the listening comprehension of L2 learners. The results showed that the participants who received the full question-preview format scored higher than those receiving either the answer-option preview or question-stem preview, despite a statistically nonsignificant difference across the three previewing activities. In addition, the participants exposed to diverse cultural texts did not perform differently in their comprehension score. The findings suggest that the use of visual cues and key-vocabulary instruction in both texts may have compromised the positive psychological value of question previewing in enhancing comprehension of the unfamiliar text.     

Ratio and product methods of estimation of population mean in the presence of correlated measurement errors

The properties of the estimators of population mean arising from the ratio and product methods of estimation in the context of sample surveys have been analyzed in this paper when the observations on both the study and auxiliary variables are contaminated with measurement errors. The measurement errors in both the variables are also correlated. The properties of the ratio and product estimators along with the sample mean under the influence of measurement errors are derived and studied. The properties of the estimators in finite samples are studied through Monte-Carlo simulation and its findings are reported.     

Geographic distance and intergenerational relationships in Chinese migrant families

ABSTRACT

This study examines the effect of adult Chinese migrants’ geographic distance from home on their intergenerational relationships with parents who remain behind. We compared monetary and family care support as well as emotional relationships among four parent-child groups: older adults and international migrant children, older adults and internal migrant children (who migrated to other cities in China), older adults and coresiding children, and older adults and local children (living in the same city as their parents). Data were derived from 332 older adults in Beijing, China, with at least one child who migrated to another country or city. Results from chi-square tests, anaylsis of variance (ANOVA) tests, and regression analyses indicate that international and internal migrant children maintain similar intergenerational relationships with their parents, and that both of those groups are less likely than coresiding and local children to have family care exchanges and emotionally close relationships with their parents. The results may help professionals develop supportive services and policies for older adults in migrant families.