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951.
A dynamic factor model is proposed for the analysis of multivariate nonstationary time series in the time domain. The nonstationarity in the series is represented by a linear time dependent mean function. This mild form of nonstationarity is often relevant in analyzing socio-economic time series met in practice. Through the use of an extended version of Molenaar's stationary dynamic factor analysis method, the effect of nonstationarity on the latent factor series is incorporated in the dynamic nonstationary factor model (DNFM). It is shown that the estimation of the unknown parameters in this model can be easily carried out by reformulating the DNFM as a covariance structure model and adopting the ML algorithm proposed by Jöreskog. Furthermore, an empirical example is given to demonstrate the usefulness of the proposed DNFM and the analysis. 相似文献
952.
The EM algorithm is a popular iterative method for estimating parameters in the latent class model where at each step the unknown parameters can be estimated simply as weighted sums of some latent proportions. The algorithm may also be used when some parameters are constrained to equal given constants or each other. It is shown that in the general case with equality constraints, the EM algorithm is not simple to apply because a nonlinear equation has to be solved. This problem arises, mainly, when equality constrints are defined over probabilities indifferent combinations of variables and latent classes. A simple condition is given in which, although probabilities in different variable-latent class combinations are constrained to be equal, the EM algorithm is still simple to apply.The authors are grateful to the Editor and the anonymous reviewers for their helpful comments on an earlier draft of this paper. C. C. Clogg and R. Luijkx are also acknowledged for verifying our results with their computer programs MLLSA and LCAG, respectively. 相似文献
953.
Mario Romanazzi 《Psychometrika》1992,57(2):237-259
The perturbation theory of the generalized eigenproblem is used to derive influence functions of each squared canonical correlation coefficient and the corresponding canonical vector pair. Three sample versions of these functions are described and some properties are noted. As particular applications, the influence function of the squared multiple correlation coefficient and influence functions of eigenvalues and eigenvectors in correspondence analysis are obtained. Three numerical examples are briefly discussed.We thank the Editor and the anonymous reviewers for their helpful comments. This research was carried out with the financial support of the Italian Ministry of the University and the National Research Council. 相似文献
954.
Jacqueline J. Meulman 《Psychometrika》1992,57(4):539-565
The recent history of multidimensional data analysis suggests two distinct traditions that have developed along quite different lines. In multidimensional scaling (MDS), the available data typically describe the relationships among a set of objects in terms of similarity/dissimilarity (or (pseudo-)distances). In multivariate analysis (MVA), data usually result from observation on a collection of variables over a common set of objects. This paper starts from a very general multidimensional scaling task, defined on distances between objects derived from one or more sets of multivariate data. Particular special cases of the general problem, following familiar notions from MVA, will be discussed that encompass a variety of analysis techniques, including the possible use of optimal variable transformation. Throughout, it will be noted how certain data analysis approaches are equivalent to familiar MVA solutions when particular problem specifications are combined with particular distance approximations.This research was supported by the Royal Netherlands Academy of Arts and Sciences (KNAW). An earlier version of this paper was written during a stay at McGill University in Montréal; this visit was supported by a travel grant from the Netherlands Organization for Scientific Research (NWO). I am grateful to Jim Ramsay and Willem Heiser for their encouragement and helpful suggestions, and to the Editor and referees for their constructive comments. 相似文献
955.
Ana D. Rivera-Tovar Paul Pilkonis Ellen Frank 《Journal of psychopathology and behavioral assessment》1992,14(2):189-199
The symptom patterns of 180 women with prospectively confirmed late luteal-phase dysphoric disorder (LLPDD) were examined using a careful application of factor and cluster analytic techniques. Factor analysis of premenstrual change scores on 33 common premenstrual syndrome symptoms yielded four orthogonal factors that were consistent across two sets of menstrual cycle data. These were a negative affect dimension with concomitant behavioral changes, physical symptoms, agitation, and positive arousal. Cluster analysis of factor scores grouped patients into one of five symptom patterns, the most common of which is a general distress cluster, characterized by symptoms across all dimensions. The LLPDD symptom groups identified are remarkably consistent with those of earlier studies using both normative and clinic samples, and consideration of symptom pattern differences in future research may greatly increase our understanding of this disorder. 相似文献
956.
Seth C. Kalichman Margretta Dwyer Margit C. Henderson Laura Hoffman 《Journal of psychopathology and behavioral assessment》1992,14(3):259-276
Multivariate clustering procedures were used to identify homogeneous subgroups of outpatient sex offenders against children (n=110)on the basis of the Minnesota Multiphasic Personality Inventory (MMPI). Results indicated a five-subgroup solution. Two within-normal-limits and two clinically elevated profile subgroups replicated subtypes found in previous cluster analytic studies of child sex offenders. The fifth subgroup appeared similar in MMPI profile pattern and elevation to a previously identified subtype of rapists. Discriminant analyses showed that subgroups differed along dimensions of cognitive disturbance and sexual functioning. Furthermore, levels of psychopathology corresponded with levels of sexual pathology. Results are discussed with reference to previous MMPI cluster analytic studies of sex offenders and theories of sexual aggression.Portions of this paper were presented at the meeting of the Midwestern Psychological Association, 1992, Chicago, Illinois. 相似文献
957.
Georgios D. Sideridis Ph.D. Charles R. Greenwood Ph.D. 《Journal of Behavioral Education》1996,6(2):203-211
Quality-control charts can be particularly useful in identifying treatment effects and patterns of behaviors in single-subject behavior-analytic experiments that cannot be determined by visual inspection of their graphs. Using an example from the behavior analysis literature the quality-control charts identified the presence of treatment effects across phases as well as the presence of trends within and between phases. The ease of their calculations suggest use of them by behavior analysts whenever the effects of particular interventions are questionable. 相似文献
958.
Jane Blake-Mortimer Anthony H. Winefield Ainsley H. Chalmers 《International journal of stress management》1996,3(4):189-207
The relationship between psychological stress and lymphocytic 5-ectonucleotidase, an enzyme marker for lymphocyte differentiation, was studied. Lymphocytic 5-ectonucleotidase was decreased significantly by about twofold in persons experiencing psychological stress, with a corresponding change in Total Mood Disturbance scores of the Profile of Mood States. Enzyme values were reversible in that they returned to normal once the stress had been reduced. Administration of high doses of ascorbate to severely depressed patients also normalized 5-ectonucleotidase activities, and implied that low enzyme values in stressed persons may be mediated by oxygen radical damage. This finding was consistent with previous reports of heightened inflammatory responses occurring in depressed patients. The primary cause of lowered 5-ectonucleotidase during stress may be the breakdown in the homeostatic mechanisms of the hypothalamic-pituitary-adrenal axis and immune system resulting in lymphoid tissue resistance to corticosteroids. It is suggested that this lowering of lymphocyte 5-ectonucleotidase may contribute to stress-mediated immune suppression by inhibiting lymphocyte maturation. 相似文献
959.
We studied the relation between the presence versus the absence of sleep deprivation or allergy symptoms and the rate and function of problem behavior. Three students whose problem behavior was negatively reinforced by escape from instruction were studied across several weeks using analogue functional analyses. Our results indicated that the extraexperimental events were associated with (a) termination of instruction functioning as a negative reinforcer, (b) increased rates of negatively reinforced problem behavior, or (c) increased rates of problem behavior across all conditions. 相似文献
960.
Jennifer J. McComas David P. Wacker Linda J. Cooper Jennifer M. Asmus David Richman Beth Stoner 《Journal of applied behavior analysis》1996,29(3):397-401
Brief multielement designs were used to examine the effects of specific instructional strategies on accuracy of academic performance during outpatient evaluations of 4 children with learning disorders. Instructional strategies that improved accuracy on academic tasks were identified for all participants. These results suggest that the application of experimental analysis methodologies to instructional variables may facilitate the identification of stimulus prompts that are associated with enhanced academic performance. 相似文献