Assessing Lund's critical values for testing for outliers in linear regression models

This note assesses Lund's critical bounds as approximations to the critical values of a size-a test for detecting single outlier in a multiple linear regression model. A Monte Carlo experiment shows that the empirical sizes are very close to the nominal sizes, and the regressors have little effect on the empirical sizes. Lund's tables are revised to higher accuracy.     

On the distribution of quadratic forms in normal random variables

This paper provides necessary and sufficient conditions for a quadratic form in singular normal random variables to be distributed as a given linear combination of independent noncentral chi-square variables. Using this result, an extension of Cochran's theorem to quadratic forms of noncentral chi-square variables is derived.     

A method of deriving valid approximate expressions for bias in ratio estimation

The expectation of a ratio of two statistics is usually obtained by the method in which the denominator is expanded into a binomial series around its mean. However, this method can less generally be employed because the expansion of the denominator is not always valid. This paper presents a device in which the expectation of a ratio of two statistics can more generally be obtained. The device is to adopt a positive value as ‘catalyzer’. It can be applied not only to the ratio of estimates based on samples but also to ratio of any two statistics, if the denominator is positive and finite.     

Changes in Americans' Policy Preferences, 1935-1979

Using responses to 3,315 survey questions asked of nationalsamples, we examine how policy preferences of Americans havechanged over the last 45 years. The data indicate that therehas been considerable stability in public opinion: responsesto half the 613 repeated policy items show no significant changeat all; approximately half the detectable changes were lessthan 10 percentage points; and rarely did preferences fluctuatesignificantly back and forth within a short time period. Foreignpolicy changes were no larger or more frequent than domestic,but they did tend to occur more abruptly. When opinion shiftsoccurred, they were not random or capricious; they were usuallyrelated to important changes in citizens' social and economicenvironments. Rapid shifts generally coincided with major eventsin international affairs or the economy.     

An Examination of the Relationship Between Absorptive Capacity and Organizational Learning,and a Proposed Integration

Since its inception, the concept of absorptive capacity has been closely linked with notions of organizational learning. Yet the precise nature of the relationship between these two concepts has never been established. This relationship is examined in a variety of ways, and it is suggested that the literature on these two concepts shares a conceptual affinity which needs to be delineated. It is suggested that absorptive capacity (a dynamic capability) is a concrete example of organizational learning that concerns an organization's relationship with new external knowledge. Using the 4I Model for organizational learning ( Crossan, M.M., Lane, H.W. and White, R.E. (1999 ). An organizational learning framework: from intuition to institution. Academy of Management Review, 24, 522–537) and Zahra and George's conceptualization of absorptive capacity ( Zahra, S.A. and George, G. (2002 ). Absorptive capacity: a review, reconceptualization, and extension. Academy of Management Review, 27, 185–203), this paper proposes an integration of the two concepts.     

Physical activity is associated with better health and psychological well-being during transition to university life

The authors investigated vigorous physical activity, psychological well-being, and self-reported illness during transition to first-year university life in a sample of 175 Canadian undergraduates. At the completion of their first year of university study, participants completed retrospective measures assessing vigorous physical activity, upper respiratory infectious illness (URI), doctor visits, as well as measures of psychological well-being. Based on nationally recommended (US Department of Health and Human Services) standards, 61% of students reported engaging in adequate levels of vigorous activity during their first year at university. The authors found no differences in URIs between sufficiently and insufficiently active students. However, insufficiently active students scored lower on psychological well-being and were twice as likely to have consulted a physician regarding an illness compared with sufficiently active students.     

Overprotection and lowered expectations of persons with disabilities: the unforeseen consequences

Lowered expectations and overprotection of the individual with a disability can cause lowered self esteem which can result in a life time of underachievement and failure to reach their full potential. Both lowered expectations and overprotection are forms of discrimination. Internalization of discrimination causes the person with a disability to believe that they are less capable than a person without a disability. Parents and care providers of children with disabilities may overprotect the child to shield them from harm; however this can actually cause more damage. Successful parenting skills are required to help children and adolescents develop a positive self concept and high self esteem. Guidelines have been developed to assist parents, educators and other professionals regarding the effects of overprotection and lowered expectations.     

家庭医生签约服务下社区居民就医选择的相关因素研究

为了解南京市浦口区居民就医选择现状,分析影响就医选择的相关因素,以浦口区11个社区卫生服务中心为调查地点,普查与等容抽样相结合方式纳入调查对象2 301人。问卷调查收集其人口学特征、就医选择以及医疗相关行为等信息;多因素Logistic回归分析浦口区居民就医选择的相关影响因素。结果显示,调查对象中1 883人（81.9%）表示可以接受以家庭医生为核心的基层首诊,1 525人（66.3%）选择首先去基层医疗机构就诊。Logistic回归分析结果显示,到最近医疗机构所需时间、年龄、慢性病、是否签约家庭医生是居民接受以家庭医生为核心的基层首诊的相关因素;影响居民就医选择的相关因素则包括到最近医疗机构所需时间、年龄、文化程度、家庭人均月收入、是否签约家庭医生。浦口区居民选择基层医疗机构首诊的构成比相对较高;签约家庭医生有助于促进社区居民对基层首诊的选择与接受度;60岁及以上老年人与慢病患者对基层首诊的需求度更高,提示签约家庭医生的推广工作应重点关注这两类人群。     

The Scale Invariant Wigner Spectrum Estimation of Gaussian Locally Self-Similar Processes

We study locally self-similar processes (LSSPs) in Silverman’s sense. By deriving the minimum mean-square optimal kernel within Cohen’s class counterpart of time–frequency representations, we obtain an optimal estimation for the scale invariant Wigner spectrum (SIWS) of Gaussian LSSPs. The class of estimators is completely characterized in terms of kernels, so the optimal kernel minimizes the mean-square error of the estimation. We obtain the SIWS estimation for two cases: global and local, where in the local case, the kernel is allowed to vary with time and frequency. We also introduce two generalizations of LSSPs: the locally self-similar chirp process and the multicomponent LSSP, and obtain their optimal kernels. Finally, the performance and accuracy of the estimation is studied via simulation.