Some contributions to efficient statistics in structural models: Specification and estimation of moment structures

Current practice in structural modeling of observed continuous random variables is limited to representation systems for first and second moments (e.g., means and covariances), and to distribution theory based on multivariate normality. In psychometrics the multinormality assumption is often incorrect, so that statistical tests on parameters, or model goodness of fit, will frequently be incorrect as well. It is shown that higher order product moments yield important structural information when the distribution of variables is arbitrary. Structural representations are developed for generalizations of the Bentler-Weeks, Jöreskog-Keesling-Wiley, and factor analytic models. Some asymptotically distribution-free efficient estimators for such arbitrary structural models are developed. Limited information estimators are obtained as well. The special case of elliptical distributions that allow nonzero but equal kurtoses for variables is discussed in some detail. The argument is made that multivariate normal theory for covariance structure models should be abandoned in favor of elliptical theory, which is only slightly more difficult to apply in practice but specializes to the traditional case when normality holds. Many open research areas are described.     

Comparing latent distributions

We consider the problem of comparingm latent population distributions when the observed values are scores on a test battery with binary items. The latent densities are assumed to be normal densities, and we consider a test for equality of the means as well as a test equality of the variances. In addition, we consider a longitudinal model, where the test battery has been applied to the same individuals at different points in time. This model allows for correlations between the latent variable at different time points, and methods are discussed for estimating the correlation coefficient.This work was supported in part by a grant from the Danish Social Science Research Council.     

Infant state in relation to its environmental context

Two neonatal intensive care units (NICU) were observed every 15 minutes for at least 72 consecutive hours. Although infants on both NICUs were exposed to considerable amounts of stimulation, there were differences between the units for each environmental measure in the amount of stimulation and/or the pattern of circadian periodicity. The two NICUs also differed in the amount of time infants spent in various states and in the pattern of state periodicity. In general, the diurnal rhythms of the infant states were associated with the diurnal rhythms of different environmental events; furthermore, the patterns of association were not the same on the two NICUs. The results point to potential problems in depicting a “typical” NICU. More importantly, they suggest that the environmental of NICUs has a recognizable influence on aspects of their inhabitants' behavior and that the nature of influence is different from NICU to NICU. The effects are potentially significant for physical, social, and cognitive development.     

Testing Process Factor Analysis Models Using the Parametric Bootstrap

Process factor analysis (PFA) is a latent variable model for intensive longitudinal data. It combines P-technique factor analysis and time series analysis. The goodness-of-fit test in PFA is currently unavailable. In the paper, we propose a parametric bootstrap method for assessing model fit in PFA. We illustrate the test with an empirical data set in which 22 participants rated their effects everyday over a period of 90 days. We also explore Type I error and power of the parametric bootstrap test with simulated data.     

From “Longshot” to “Fantasy”: Obligations to Pediatric Patients and Families When Last-Ditch Medical Efforts Fail

Clinicians at quaternary centers see part of their mission as providing hope when others cannot. They tend to see sicker patients with more complex disease processes. Part of this mission is offering longshot treatment modalities that are unlikely to achieve their stated goal, but conceivably could. When patients embark on such a treatment plan, it may fail. Often treatment toward an initial goal continues beyond the point at which such a goal is feasible. We explore the progression of care from longshot to fantasy using two pediatric cases. This progression may be differentiated into four distinct stages of care related to the potential of achieving the initial goals of care. Physicians are often ill prepared for the progression of treatments from a longshot hope to an unfeasible and, therefore, typically unjustified intervention. We present a structured approach to guide clinicians at referral institutions where these situations may be common. The transition of care from “longshot” to “fantasy” is an inherent part of quaternary care for the sickest of patients that has been underexplored. Physicians are often poorly equipped to approach that transition. We advocate this approach to the shift from longshot to fantasy with the belief that such a structured method will have multiple benefits, including: reduced suffering for the patient; decreased emotional burden on patient and family; decreased provider moral distress; increased likelihood of seeking high quality palliative care earlier; and provision of honest and straightforward information to patients and their families.     

ICU医护沟通与协作的现状与思考

许多研究表明ICU医护之间的沟通与协作存在重大问题,特别是在临终决策中存在分歧。护士的作用经常被忽视。加强医护之间的沟通与协作有助于提高医疗质量并改善医护、患者及家庭满意度。许多旨在改善沟通与协作的措施已经证实有效并可应用于临床实践,并应对此进行更深一步的研究。     

Overshadowing by fixed- and variable-duration stimuli

Two experiments investigated the effect of the temporal distribution form of a stimulus on its ability to produce an overshadowing effect. The overshadowing stimuli were either of the same duration on every trial, or of a variable duration drawn from an exponential distribution with the same mean duration as that of the fixed stimulus. Both experiments provided evidence that a variable-duration stimulus was less effective than a fixed-duration cue at overshadowing conditioning to a target conditioned stimulus (CS); moreover, this effect was independent of whether the overshadowed CS was fixed or variable. The findings presented here are consistent with the idea that the strength of the association between CS and unconditioned stimulus (US) is, in part, determined by the temporal distribution form of the CS. These results are discussed in terms of time-accumulation and trial-based theories of conditioning and timing.     

Clarifying Amateurism: A Logical Approach to Resolving the Exploitation of College Athletes Dilemma

In this paper we investigate the logical consequences of the common understanding of amateurism in the context of big-time US college athletics, and in so doing, illustrate a method based on linguistic analysis and logic. The initial thrust of the paper centres on the term ‘amateur’ as presupposed by the late Professor Brand in his attempt to justify the ‘business’ of NCAA-sponsored Division I sports by decoupling the ‘participants from the enterprise’. Next, we examine a more rigorous definition of the term ‘amateur’ in order to show more clearly the difficulties posed by the current situation in college athletics. Additionally, our use of linguistic analysis exposes a flaw in the NCAA's recent move to amend by-law 12.02 in an attempt to avoid the charge of exploitation. Lastly, we put forth a new proposal for better dealing with the central issues swirling around the NCAA as it strives to formulate sound policy at this ‘tectonic’ juncture of players, fans, college programmes and academic integrity.     

礼与食孰重:儒墨之辩新论

孔墨“俱道尧舜”但政治理想却截然不同,其主要原因在于两方面,首先是他们有着各不相同的历史传统和政治理想,其次是他们对于中国轴心时代的社会现实有着完全不同的认识和评价。两家显学的根本分歧在于“礼与食孰重”,儒家认为生活资料的匮乏是由于人的动物性欲望未能得到有效的遏制,因而特别强调了一整套礼仪制度对于文明的重要性。墨家则认为正是由于礼仪制度本身的维系严重消耗了社会的物质基础,才使得人们为了满足饥饿的食本能而不得不弱肉强食。这个思想史的问题至今仍未结束。     

Commodious Axiomatization of Quantifiers in Multiple-Valued Logic

We provide tools for a concise axiomatization of a broad class of quantifiers in many-valued logic, so-called distribution quantifiers. Although sound and complete axiomatizations for such quantifiers exist, their size renders them virtually useless for practical purposes. We show that for quantifiers based on finite distributive lattices compact axiomatizations can be obtained schematically. This is achieved by providing a link between skolemized signed formulas and filters/ideals in Boolean set lattices. Then lattice theoretic tools such as Birkhoff's representation theorem for finite distributive lattices are used to derive tableau-style axiomatizations of distribution quantifiers.