Laplace-normal mixtures fitted to wind shear data

A mixture model with Laplace and normal components is fitted to wind shear data available in grouped form. A set of equations is presented for iteratively estimating the parameters of the model using an application of the EM algorithm. Twenty-four sets of data are examined with this technique, and the model is found to give a good fit to the data. Some hypotheses about the parameters in the model are discussed in light of the estimates obtained.     

Do bootstrap confidence procedures behave well uniformly in P?

An important statistical problem is to construct a confidence set for some functional T(P) of some unknown probability distribution P. Typically, this involves approximating the sampling distribution J_n(P) of some pivot based on a sample of size n from P. A bootstrap procedure is to estimate J_n(P) by J_n(&Pcirc;_n), where P?_n is the empirical measure based on a sample of size n from P. Typically, one has that J_n(P) and J_n(P?_n) are close in an appropriate sense. Two questions are addressed in this note. Are J_n(P) and J_n(P?_n) uniformly close as P varies as well? If so, do confidence statements about T(P) possess a corresponding uniformity property? In the case T(P) = P, the answer to the first questions is yes; the answer to the second is no. However, bootstrap confidence statements about T(P) can be made uniform over a restricted, though large, class of P. Similar results apply to other functional T(P).     

Macroeconomic conditions, institutional factors and demographic structure: What causes welfare caseloads?

Some of the possible determinants of changes observed in welfare caseloads are analysed in this study. The paper attempts to explain variations in welfare caseloads on the basis of four different factors: macroeconomic conditions, interactions with other income maintenance programmes, changes in the programme's parameters and changes in the demographic structure. Different models are tested by applying time series techniques. The data employed are of an administrative nature and cover the whole period that the Madrid programme has been in operation. The results show that the effects of both unemployment and institutional variables are strong and significant. Macroeconomic effects on caseloads could be offset or reinforced by changes in unemployment protection and reforms of the programme's parameters. The significant effects found for the share of lone-parent applicants also show that demographic shifts could shape the trends of welfare rolls regardless of the changes in unemployment or the implementation of institutional reforms. The authors would like to thank Juan Gabriel Rodríguez, Minoru Kunizaki, Miguel Angel Malo and three anonymous referees for their comments and suggestions. Financial and technical support from the Spanish Institute for Fiscal Studies, the Inter-ministerial Commission on Science and Technology (SEC 2001-0746) and the Social Services Department of the Madrid Government is also gratefully acknowledged. Responsible editor: Christian Dustmann.     

Acting out in children: A review of the literature

This paper presents a review of the literature on the meaning, etiology and categorization of acting out symtomatology in children. It is apparent that there is no one cause nor is there one well defined disorder.DSM-III categories as they relate to behavior disorders are discussed and the problems of diagnosis are addressed. Appropriate treatment goals and interventions cannot be developed unless more global aspects of a child's functioning and the environment in which he lives are assessed.