Updating formulae for the sample covariance and correlation

This article provides an easy derivation of updating formulae for the sample covariance and, by extension, for the Pearson product–moment correlation coefficient.     

由线性递推公式求数列的通项

由线性递推公式求数列的通项,在高中数学考试,大学数学考试经常出现。特别是计算机软件设计中应用更是广泛。本文就高考数学中出现的线性递推公式求数列的通项的问题,通过初等数学和高等数学来解决。体会它们的相同和差异特点。     

递归数列通项与不动点原理

运用线性空间的不动点原理,研究了几类递归数列通项问题,获得了求三类递归数列通项公式的一种新方法。     

利用母函数法解一类递推关系

文[1]用特征根法求解了一类递推关系,本文给出了一种新方法———利用母函数法求解一类递推关系,并且从理论上和实例中进行了具体的研究和尝试.     

几类一阶递推数列的通项公式的求法

数列的通项公式的求法是数学学习中的一个重要内容,文章对一阶递推数列的通项公式给出几种类型的求法,这对学生的数学学习具有一定的指导作用。     

The complexity of child protection recurrence: The case for a systems approach

ObjectiveResearch on child protection recurrence has found consistent child, family, and case characteristics associated with repeated involvement with the child protection system. Despite the considerable body of empirical research, knowledge about why recurrence occurs, and what can be done to reduce it, is limited.MethodThis paper reviews the empirical literature and analyses the approaches of prior recurrence research. Four related conceptual challenges are identified: (1) a tendency to conflate child protection recurrence with repeated child maltreatment; (2) uncertainty about how best to operationalize and measure child protection recurrence in research; (3) inconsistency between prevailing explanations for the most frequently observed patterns of recurrence; and (4) difficulty in developing coherent strategies to address child protection recurrence based on research.ResultsAddressing these challenges requires a greater consideration of the effects of decision-making in the child protection system on recurrence. This paper proposes a methodology based in systems theory and drawing on existing administrative data to examine the characteristics of the child protection system that may also produce recurrence.     

递归函数的模拟

介绍了一种通用的可以将Turbo C中一般递归函数转换为非递归函数变化规则。     

Risk of re-report: A latent class analysis of infants reported for maltreatment

A key challenge facing child protective services (CPS) is identifying children who are at greatest risk of future maltreatment. This analysis examined a cohort of children with a first report to CPS during infancy, a vulnerable population at high risk of future CPS reports. Birth records of all infants born in California in 2006 were linked to CPS records; 23,871 infants remaining in the home following an initial report were followed for 5 years to determine if another maltreatment report occurred. Latent class analysis (LCA) was used to identify subpopulations of infants based on varying risks of re-report. LCA model fit was examined using the Bayesian information criterion, a likelihood ratio test, and entropy. Statistical indicators and interpretability suggested the four-class model best fit the data. A second LCA included infant re-report as a distal outcome to examine the association between class membership and the likelihood of re-report. In Class 1 and Class 2 (lowest risk), the probability of a re-report was 44%; in contrast, the probability in Class 4 (highest risk) was 78%. Two birth characteristics clustered in the medium- and highest-risk classes: lack of established paternity and delayed or absent prenatal care. Two risk factors from the initial report of maltreatment emerged as predictors of re-report in the highest-risk class: an initial allegation of neglect and a family history of CPS involvement involving older siblings. Findings suggest that statistical techniques can be used to identify families with a heightened risk of experiencing later CPS contact.     

The efficacy of family reunification practices: reentry rates and correlates of reentry for abused and neglected children reunited with their families

OBJECTIVE: Since the 1980s Child Protective Services has increasingly relied on family reunification for abused/neglected children rather than long term foster care or adoption. While family reunification practices are controversial, little research is available to inform the debate. This research explores the efficacy of these practices. METHODS: This study utilizes two CPS data sources and both quantitative and qualitative methodologies to identify reentry rates and correlates of reentry for abused and neglected children returned to their families by CPS. RESULTS: System reentry due to additional maltreatment is considerable. Thirty-seven percent of the children reunited with their families reenter the system within 3 1/2 years. Correlates of reentry are identified as; abuse type, CPS history, parental competency, race, criminal history, substance abuse, and social support. Notably, assessments of risk made by caseworkers are found to be unrelated to reentry. CONCLUSIONS: The high reentry rate and the limitations of current risk assessment procedures suggest that CPS family reunification practices have not been entirely successful. The identification of specific risks of reentry, such as those revealed in this study, will be helpful in assessing risk on cases. In addition, future studies should explore the systemic deficiencies that contribute to the additional maltreatment that occurs for a sizable proportion of the children served by the system.     

解读《拉格泰姆时代》历史的重现与重构

从新历史主义的视角剖析,E．L．多克托罗的《拉格泰姆时代》烙有“文本的历史性”这一显著特点。该文本不仅反映了其所处历史时期的社会文化状况,还参与创造了作者所处时代的思想文化历史,形成了新历史主义所认为的文学和历史的那种互文关系,展示了历史真实与文学虚构相结合的新历史主义文本的特点。