Second-order asymptotic loss of the MLE of a truncation parameter for a truncated exponential family of distributions

For a truncated exponential family of distributions with a truncation parameter γ and a natural parameter θ as a nuisance parameter, the stochastic expansions of bias-adjusted maximum likelihood estimators and of γ when θ is known and when θ is unknown, respectively, are derived. The second-order asymptotic loss of relative to is also obtained through their asymptotic variances. Further, some examples are given

The Asymptotic Bound by the Kiefer-Type Information Inequality and Its Attainment

In non-regular cases when the regularity conditions does not hold, the Chapman–Robbins (1951) inequality for the variance of unbiased estimators is well known, but the lower bound by the inequality is not attainable. In this article, we extend the Kiefer-type information inequality applicable to the non-regular case to the asymptotic situation, and we apply it to the case of a family of truncated distributions, in which the lower bound by the Kiefer-type inequality derived from an appropriate prior distribution is attained by the asymptotically unbiased estimator. It also follows from the completeness of the sufficient statistic that the lower bound is asymptotically best. Some examples are also given

A Higher Order Approximation to a Percentage Point of the Distribution of a Noncentral t-Statistic Without the Normality Assumption

Noncentral distributions appear in two sample problems and are often used in several fields, for example, in biostatistics. A higher order approximation for a percentage point of the noncentral t-distribution under normality is given by Akahira (1995) and is also shown to be numerically better than others. In this article, without the normality assumption, we obtain a higher order approximation to a percentage point of the distribution of a noncentral t-statistic, in a similar way to Akahira (1995) where the statistic based on a linear combination of a normal random variable and a chi-statistic takes an important role. Its application to the confidence limit and the confidence interval for a noncentrality parameter are also given. Further, a numerical comparison of the higher order approximation with the limiting normal distribution is done and the former one is shown to be more accurate. As a result of the numerical calculation, the higher order approximation seems to be useful in practical situations, when the size of sample is not so small.Journal online　著者版(author)　Table 1　⇒　Table 4.1　Table 2　⇒　Table 4.2　Table 3　⇒　Table 4.3　Table 4　⇒　Table 4.4　Table 5　⇒　Table 4.5　Table 6　⇒　Table 4.6　Table 7　⇒　Table 4.7　Table 8　⇒　Table 4.8　Table 9　⇒　Table 5.1　Table 10　⇒　Table 5.2　Table 11　⇒　Table 5.

A Meta-Analysis of Interleukin-8 -251 Promoter Polymorphism Associated with Gastric Cancer Risk

Background: Potential functional allele A/T single nucleotide polymorphism (SNP) of Interleukin 8 (IL-8) promoter-251has been implicated in gastric cancer risk. Methods: We aimed to explore the role of A/T SNP of IL-8-251 in the susceptibility to gastric cancer through a systematic review and meta-analysis. Each initially included article was scored for quality appraisal. Desirable data were extracted and registered into databases. Eighteen studies were ultimately eligible for the meta-analysis of IL-8- 251 A/T SNP. We adopted the most probably appropriate genetic model (codominant model). Potential sources of heterogeneity were sought out via stratification and sensitivity analyses, and publication biases were estimated. Results: Between IL-8-251 AA genotype with gastric cancer risk, statistically significant association could be noted with overall gastric cancer, evidently noted in Asians, witnessed in high quality subgroup, and apparently noted in intestinal-type gastric cancer. Conclusions: Our meta-analysis indicates that IL-8-251 AA genotype is associated with the overall risk of developing gastric cancer and may seem to be more susceptible to overall gastric cancer in Asian populations. IL-8-251 AA genotype is more associated with the intestinal-type gastric cancer. IL-8-251 AA genotype is not associated with Helicobacter Pylori infection status in our meta-analysis

The polymorphism interleukin 8 −251 A/T influences the susceptibility of Helicobacter pylori related gastric diseases in the Japanese population

Background: Helicobacter pylori infection is associated with variable clinical outcomes, including gastroduodenal diseases, and genetic factors may be relevant in this process. Aims: We investigated the effects of an interleukin 8 (IL-8) gene polymorphism on the risk of gastroduodenal diseases, the degree of H pylori induced gastritis, and IL-8 gene transcription. Subjects: The study was performed in 244 healthy control subjects and 690 H pylori positive patients with non-cardia gastric cancer, gastric ulcer, duodenal ulcer, or gastritis. Methods: We identified the IL-8 −251 A/T polymorphism by direct sequence analysis, and measured the gastritis score and serum pepsinogen (PG). The transcriptional promoter activity of the IL-8 gene was assessed by luciferase assay. Results: IL-8 −251A was associated with a higher risk of gastric cancer and gastric ulcer. Patients carrying IL-8 −251A showed an increased risk of gastric cancer (odds ratios (OR) 2.01 (95% confidence interval (CI) 1.38–2.92)) and gastric ulcer (OR 2.07 (95% CI 1.37–3.12)). Compared with patients younger than 49 years, atrophy and metaplasia scores in the antrum were significantly higher and the PG I/II ratio significantly lower in −251A carriers than in T/T carriers. In the in vitro assay, IL-8 −251A showed enhanced promoter activity in response to IL-1β or tumour necrosis factor α. Conclusions: The IL-8 −251A allele may be associated with progression of gastric atrophy in patients with H pylori infection, and may increase the risk of gastric cancer and gastric ulcer in Japanese people