TESTING SPHERICITY UNDER A MIXTURE MODEL

The robustness of Mauchly's sphericity test criterion when sampling from a mixture of two multivariate normal distributions is studied. The distribution of the sphericity test criterion when the sample covariance matrix has a non-central Wishart density of rank one is derived in terms of Meijer's G-functions; its distribution under the mixture model is then deduced. The robustness is studied by computing actual significance levels of the test under the mixture model using the critical values under the usual normal model.     

Children's gender- and age-based categorization in similarity and induction tasks

The present studies examined children's and adults' preferences for gender- or age-based categorization using similarity and inductive inference tasks. Four-year-olds, 6-year-olds, and adults looked at pictures of people and decided which of two was more like a target (similarity condition) or which shared a novel age- or gender-related property with the target (inference condition). Age or gender-based matches were possible. The results are consistent with previous findings that gender-based classification decreases with age. However, they also demonstrate that children use gender more for judging similarity than for making inferences about novel properties. Distinct patterns emerge from the two tasks: 6-year-olds and adults in both conditions categorize more by age than gender; 4-year-olds categorize by gender more than age in the similarity task, but by age more in the induction task. Only adults differentiated by property in the inference condition. These findings suggest that the salience of gender categories cannot entirely be attributed to their inductive potential. Gender has a salience beyond what would be predicted by its power for directing novel generalizations.     

Estimation of noncentrality parameters

We propose some estimators of noncentrality parameters which improve upon usual unbiased estimators under quadratic loss. The distributions we consider are the noncentral chi-square and the noncentral F. However, we give more general results for the family of elliptically contoured distributions and propose a robust dominating estimator.     

Weakly implementable social choice rules

Previous investigations have shown that a social choice function which is partially implementable must be characterized by pervasive veto power. This paper investigates how much additional latitude in the design of social choice functions, and how much relief from this vetoers result, can be achieved by examining multi-valued social choice rules and relaxing the requirement of partial implementability to a requirement that we call weak partial implementability. We find that the power structures which characterize partially implementable social choice functions, including the veto properties, also characterize weakly partially implementable social choice rules. The conclusion is that invoking multi-valuedness and implementation of appealing social choice rules in strong Nash equilibria. Our results apparently exhaust the possibilities for implementation in strong Nash equilibrium. If any implementation possibility results are to be achieved, they can apparently come only by weakening the equilibrium requirement.     

The Micro System of Deviance in Intimate Relationships*

Deviance in intimate relationships may lie as much within the micro system of such relationships as it does within the personalities of the actors involved. Using a Parsonsian framework, it is argued that the strain of systemically disequilibrated relationships can produce deviant personality adaptations which, in turn, intensify conflict and deviance in those relationships. It is also proposed that a reciprocal quality exists to such maladaptations, with each member of the dyad contributing to the amplification of a stable system of deviant behavior patterns within the relationship. Because the patterns of maladaptive dyads spill over into parent-child relationships, they have implications for understanding intergenerational transmission of deviance between intimates.     

Effects of Medicaid managed care policies on mental health service use among a national probability sample of children in the child welfare system

Children in the child welfare system are dependent upon Medicaid to finance services for their considerable mental health needs. This study examines the effects of Medicaid policies on mental health service use among a national probability sample of children in the child welfare system. Data for this study came from the National Survey of Child and Adolescent Well-Being, the Caring for Children in Child Welfare study, and the Area Resource File. Weighted multivariate logistic regression analyses were conducted to estimate effects of policy variables on children's use of mental health services, controlling for child-level covariates and county-level health resources. Children in counties with behavioral carve-outs under Medicaid managed care had lower odds of inpatient mental health service use. Medicaid managed care enrollment and variations in type of provider reimbursement did not affect use of mental health services. Older age, greater need for mental health services, and higher levels of caregiver education were associated with increased odds of service use. Restrictions on use of inpatient mental healthcare caused by behavioral carve-outs may disproportionately affect children in the child welfare system who have high rates of such use. Careful adoption of carve-outs is necessary to assure appropriate care for these children.     

How Welfare Policies Affect Adolescents' School Outcomes: A Synthesis of Evidence From Experimental Studies

Using data from 8 random assignment studies and employing meta‐analytic techniques, this article provides systematic evidence that welfare and work policies targeted at low‐income parents have small adverse effects on some school outcomes among adolescents ages 12 to 18 years at follow‐up. These adverse effects were observed mostly for school performance outcomes and occurred in programs that required mothers to work or participate in employment‐related activities and those that encouraged mothers to work voluntarily. The most pronounced negative effects on school outcomes occurred for the group of adolescents who had a younger sibling, possibly because of the increased home and sibling care responsibilities they assumed as their mothers increased their employment.     

Vulnerability and Agenda: Context and Process in Project Management

This paper explores how the project management role is conditioned by the context in which change is progressed. The argument draws on Pettigrew's (1985, 1987) contextual and processual view of change, a view which does not clarify the management implications of contextual variation. Using data from a two-stage research design combining diary and survey methods, four context dimensions are identified, concerning ‘interlocking’, ‘shifting sands’, ‘ownership’ and ‘senior management view’. For analytical purposes, two extreme contexts are characterized as exposing the project manager to high and low levels of ‘vulnerability’ respectively. Project management literature typically offers a rational-linear account of change, and concentrates on ‘content’ and ‘control’ agendas, concerning technical expertise on the one hand, and planning, budgeting and monitoring techniques on the other. Sociological analyses reveal the limitations of the rational-linear account, and focus on the political and cultural dimensions of the ‘process’ agenda. The data suggest how contextual variation affects the relative priority of these agendas. The management implications of these findings are explored, for project management selection, career progression, and the development of diagnostic skills and ‘agenda management’ strategies.     

Student perceptions of the danger of drug use: a factor analysis.

Australian secondary school students from three Year levels were asked to rate the danger involved in various uses of alcohol, tobacco, inhalants, marijuana and other illicit drugs. These ratings were then factor analyzed for each Year level. The results showed a more refined discrimination among the older students, with type of drug and frequency of use being important considerations. Familiarity was a major consideration for the younger students. The cognitive factors derived from the data are consistent with expectations based on the gateway theory of drug use.