On testing hypotheses regarding a class of covariance structures

Let x be ap-component random variable having a multivariate normal distribution with covariance matrix . In this paper, we consider the problem of testing hypotheses of the formH ₀: =b ₁₁ + +b _{m m} , whereb _i 's are unknown scalars, and _i 's are a set of known and simultaneously diagonalizable matrices. This problem has both psychometric and statistical interest, and its basic theory is developed here. Besides, the problem of obtaining likelihood-ratio statistic for testingH ₀ is studied, and the statistic obtained in a special case.     

Dementia and the Neurovirulence of HIV-1

Infection with human immunodeficiency virus type 1 (HIV-1) leads rapidly to infection of the brain and subsequent neuropsychological impairment, including subclinical impairment, minor cognitive-motor disorder, and HIV-1-associated dementia (HAD). This article reviews HAD and the factors involved in its pathogenesis; the effectiveness of antiretroviral therapy; the prevalence of HIV-1 and subtypes; and the role of chemokines and cytokines as the capstones associated with neuropathology due to inflammation.     

Up-regulating positive emotions in everyday life: Strategies, individual differences, and associations with positive emotion and well-being

This research aimed to identify strategies people use to up-regulate positive emotions, and examine associations with personality, emotion regulation, and trait and state positive experience. In Study 1, participants reported use of 75 regulation strategies and trait emotional experience. Principal component analysis revealed three strategy domains: engagement (socializing, savoring), betterment (goal pursuit, personal growth), and indulgence (substance use, fantasy). In Study 2, participants reported state-level regulation and emotional experience. Engagement correlated with greater state and trait positive emotion, and overall greater well-being. Betterment correlated with less state, but greater trait, positive emotion. Indulgence correlated with greater state, but less trait positive emotion and overall lower well-being. This research suggests trade-offs between short-term and long-term emotional consequences of different strategies.     

An exploration of the Indian mindset

Eight hundred and twenty-nine adults, drawn from 12 locations in all four parts of India, participated in a study that explored the joint effects of Indians’ discrepant mindset, context sensitivity, and quality of environment on their modes of behavior. Respondents also predicted how a person is likely to change his behavior when the conditions in which he works change from disabling to enabling. The findings showed that the two most dominant modes of behavior-self-serving calculative and achieving high positive goal — coexisted, but were differently caused. Context sensitivity facilitated both modes of behavior; but adequate infrastructure and friendly and helpful people in the neighborhood encouraged only achieving high positive goal behavior. On the contrary, duplicity in professing desirable but acting under realistic compulsions, poor quality of environment, and low levels of development were conducive to self-serving calculative behavior. As a situation changed from disabling to enabling, a person was likely to shift towards more positive behavior.     

Ab initio investigation of electron-phonon interaction in LaSn3 and CaSn3

ABSTRACT

We present results for the structural, electronic, vibrational, and electron-phonon coupling properties of LaSn₃ and CaSn₃ adopting the simple cubic AuCu₃-type structure obtained using the the generalised gradient approximation of the density functional theory and plane wave ab initio pseudopotential method. Our electronic results show that both materials display metallic character with several bands, which have mainly Sn 5p character, crossing the Fermi level. The calculated phonon spectrum of LaSn₃ accords very well with reported experimental measurements. The weights of the peaks in the Eliashberg spectral function of both compounds are enhanced with the use of experimental lattice constant in our electron-phonon calculation, increasing the value of average electron phonon coupling parameter from 0.876 to 0.937 for LaSn₃ (by 7%) and from 0.642 to 0.725 for CaSn₃ (by 13%). The use of experimental lattice constant also improves the agreement between theoretical and experimental values of the superconducting temperature for both compounds.     

Debiasing Using Decomposition: The Case of Memory‐Based Credit Card Expense Estimates

This article develops a conceptual framework to examine how consumers incorporate memory‐based and context‐based cues in estimating past and future credit card expenses. Focusing on memory‐based information, in this framework we suggest that past credit card expenses may be recalled as holistic totals or episodic individual expenses depending on the accessibility of each form of expense. We tested the conceptual framework with 3 studies. Study 1 showed that the recency of past expenses and frequency of credit card usage moderated the extent to which past expenses were used in estimating future expenses. Study 1 also showed that self‐awareness of estimation bias affected consumers’ estimates of future expenses. Study 2 showed that a decomposition strategy (unbundling a total into subcategories), which serves to make episodic individual expenses more accessible, was effective in reducing sampling‐based bias. Study 3 provided a validity check and showed that decomposition cues reduced estimation errors and affected estimates of future expense. In this article, we demonstrate the manner in which memory‐based information is used to make estimates, and we also demonstrate the effectiveness of decomposition as a debiasing technique for past and future estimates.     

Interpersonal trust and organizational citizenship behavior

This study investigates the relationship between certain individual level determinants of interpersonal trust and its impact on organizational citizenship behavior. The participants (N=303) were top, middle, and lower level executives from manufacturing and services sectors. The results indicate that interaction frequency, consistency, and competence are significant predictors of interpersonal trust. Interpersonal trust is positively associated with organizational citizenship behavior, and it also partially mediated the relationship between individual level factors and organizational citizenship behavior. The results imply that the development of trust at the interpersonal level may be used as a strategy to motivate the employees to engage in extra role behaviors to ensure improved individual and organizational performance.     

Attachment, Marital Satisfaction, and Divorce During the First Fifteen Years of Parenthood

This study examines two overlapping longitudinal samples of U.S. couples with children, covering a period of 15 years after the first child's birth. The first sample extended from the pregnancy with a first child until that child was 5.5 years old; the second from ages 4.5 to 14.5. Growth curve analyses revealed that marital satisfaction declined over 15 years for both husbands and wives. Attachment security measured in the second sample was associated with greater marital satisfaction, but did not buffer against declines in marital satisfaction over time. Husbands' lower initial level of marital satisfaction measured around the first child's transition to school was the only significant predictor of marital dissolution. The discussion emphasizes theoretical and practical implications of these findings.     

On a new property of partially balanced association schemes useful in psychometric structural analysis

In an earlier paper [Psychometrika,31, 1966, p. 147], Srivastava obtained a test for the HypothesisH ₀ : = ₀₀ + ... + _ll, where i are known matrices,i are unknown constants and is the unknown (p ×p) covariance matrix of a random variablex (withp components) having ap-variate normal distribution. The test therein was obtained under (p ×p) covariance matrix of a random variablex (withp components) the condition that ₀, ₁, ..., l form a commutative linear associative algebra and a certain vector, dependent on these, has non-negative elements. In this paper it is shown that this last condition is always satisfied in the special situation (of importance in structural analysis in psychometrics) where ₀, ₁, ..., l are the association matrices of a partially balanced association scheme.This research was partially supported by the U. S. Air Force under Grant No. AF33(615)-3231, monitored by the Aero Space Research Labs.Now at Colorado State University.     

An estimation of true scores in the case of items scored on a continuous scale

For the tests in which the score on an item is not restricted to 0 and 1, but is any number on a continuous scale, a procedure for estimating an examinee's true score is given. For the case of 0, 1 item scoring this problem was considered by Lord [1959]. Following Lord, the least squares estimation procedure is used and the regression coefficient is obtained, which is compared with the generalized KR(20) and KR(21) formulas. Also, results are discussed using analysis of variance models.Now at Brooklyn College of the City University of New York.