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In longitudinal studies, investigators often measure multiple variables at multiple time points and are interested in investigating individual differences in patterns of change on those variables. Furthermore, in behavioral, social, psychological, and medical research, investigators often deal with latent variables that cannot be observed directly and should be measured by 2 or more manifest variables. Longitudinal latent variables occur when the corresponding manifest variables are measured at multiple time points. Our primary interests are in studying the dynamic change of longitudinal latent variables and exploring the possible interactive effect among the latent variables. Much of the existing research in longitudinal studies focuses on studying change in a single observed variable at different time points. In this article, we propose a novel latent curve model (LCM) for studying the dynamic change of multivariate manifest and latent variables and their linear and interaction relationships. The proposed LCM has the following useful features: First, it can handle multivariate variables for exploring the dynamic change of their relationships, whereas conventional LCMs usually consider change in a univariate variable. Second, it accommodates both first- and second-order latent variables and their interactions to explore how changes in latent attributes interact to produce a joint effect on the growth of an outcome variable. Third, it accommodates both continuous and ordered categorical data, and missing data. 相似文献
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The learning effects due to test and study trials after the initial presentation were examined in a paired‐associate learning paradigm. In Experiment 1 both the spacing and retention intervals were systematically varied. The results showed advantages of spacing for both test and study trials. However, the spacing function of test trials interacted significantly with the retention interval. At a short retention interval, the second recall was a decreasing function of spacing and paralleled closely the initial recall. As the retention interval increased, the spacing‐of‐test function assumed an inverted U‐shape. Performance after repeated studies was on the average better than after test trials. Experiment 2 confirmed that when an initial presentation was followed by two test trials, an increasing spacing interval between each successive test trial produced optimal long‐term performance. In the case where a second study trial was coupled with a test trial, a pattern with equal interval length was better than other spacing patterns. The proportion of test trials of the study list was also varied among groups of subjects. A higher proportion of test trials resulted in better final recall. 相似文献
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PROBLEM: Greater awareness of the role of parental substance abuse in child maltreatment makes it imperative that the substance abuse treatment and child welfare systems coordinate services for these parents. Yet little is known about the characteristics of child-welfare involved parents (primarily mothers) who enter into substance abuse treatment. This paper compares the characteristics of mothers in substance abuse treatment who were and were not involved with child welfare services, and discusses the treatment implications of these differences. METHOD: Data were obtained from a statewide treatment outcome monitoring project in California. Clients were assessed at treatment admission using the Addiction Severity Index. Bivariate analyses and multivariate logistic regression were conducted comparing mothers who were (N=1,939) and were not (N=2,217) involved with child welfare. RESULTS: Mothers who were involved with child welfare were younger, had more children, and had more economic problems. They were more likely to be referred by the criminal justice system or other service providers, to have a history of physical abuse, and to be treated in outpatient programs. They had lower levels of alcohol severity, but did not differ with regard to psychiatric severity or criminal involvement. Primary users of methamphetamine were disproportionately represented among this group and had a distinct profile from primary alcohol- and opiate-users. CONCLUSION: Study findings suggest that mothers involved with child welfare enter substance abuse treatment through different avenues and present a clinical profile of treatment needs related to exposure to physical abuse, economic instability, and criminal justice involvement. 相似文献
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