A p-value for testing the equivalence of the variances of a bivariate normal distribution

A p-value is developed for testing the equivalence of the variances of a bivariate normal distribution. The unknown correlation coefficient is a nuisance parameter in the problem. If the correlation is known, the proposed p-value provides an exact test. For large samples, the p-value can be computed by replacing the unknown correlation by the sample correlation, and the resulting test is quite satisfactory. For small samples, it is proposed to compute the p-value by replacing the unknown correlation by a scalar multiple of the sample correlation. However, a single scalar is not satisfactory, and it is proposed to use different scalars depending on the magnitude of the sample correlation coefficient. In order to implement this approach, tables are obtained providing sub-intervals for the sample correlation coefficient, and the scalars to be used if the sample correlation coefficient belongs to a particular sub-interval. Once such tables are available, the proposed p-value is quite easy to compute since it has an explicit analytic expression. Numerical results on the type I error probability and power are reported on the performance of such a test, and the proposed p-value test is also compared to another test based on a rejection region. The results are illustrated with two examples: an example dealing with the comparability of two measuring devices, and an example dealing with the assessment of bioequivalence.     

No landward movement: examining 80 years of population migration and shoreline change in Louisiana

Population and Environment - Louisiana lost nearly 5,000 km2 of its coastal land area due to relative sea level rise (including local, regional, and global factors driving relative sea level...     

A bootstrap approximation to the joint distribution of sum and maximum of a stationary sequence

This paper establishes the asymptotic validity for the moving block bootstrap as an approximation to the joint distribution of the sum and the maximum of a stationary sequence. An application is made to statistical inference for a positive time series where an extreme value statistic and sample mean provide the maximum likelihood estimates for the model parameters. A simulation study illustrates small sample size behavior of the bootstrap approximation.     

Impact of Migration on Kerala's Economy and Society

This article reports results of the first migration study covering the entire State of Kerala. It encompasses both measurement as well as analysis of the various types and facets of migration. Migration has been the single most dynamic factor in an otherwise dreary development scenario in Kerala during the last quarter of the twentieth century. Kerala is approaching the end of the millennium with a little cheer in many people's homes as a result of migration which has contributed more to poverty alleviation than any other factor, including agrarian reforms, trade union activities and social welfare legislation. The study shows that nearly 1.5 million Keralites now live outside India. They send home more than Rs.4,000 million a year by way of remittances. Three‐quarters of a million former emigrants have come back. They live mostly on savings, work experience, and skills acquired while abroad. More than a million families depend on an internal migrant's earnings for subsistence, children's education and other economic requirements. Whereas the educationally backward Muslims from the Thrissur‐Malappuram region provide the backbone of emigration, it is the educationally forward Ezhawas, Nairs and Syrian Christians from the former Travancore‐Cochin State who form the core of internal migration. The article also analyses the determinants and consequences of internal and external migration. It offers suggestions for policy formulation directed at optimum utilization of remittances sent home by emigrants and the expertise brought back by the return migrants. Migration in Kerala began with demographic expansion, but it will not end up with demographic contraction. Kerala has still to develop into an internally self‐sustaining economy. The prevailing cultural milieu in which its people believe that anything can be achieved through agitation, and any rule can be circumvented with proper political connections, must change and be replaced by a liberalized open economy with strict and definite rules of the game.     

Correlates in Children's Experiences of Parents' Racial Socialization Behaviors

This study examined racial socialization processes among 94 African American parents of third‐, fourth‐, and fifth‐grade children as they were predicted by children's ethnic identity exploration and unfair treatment as well as by parents' ethnic identity and discrimination experiences. Findings indicated that children's ethnic identity exploration and parents' perceptions that their children had been treated unfairly by an adult because of their race were both significantly associated with the frequency of messages to children regarding discrimination (Preparation for Bias). Parents' perceptions of children's unfair treatment from an adult and children's perceptions that they had been treated unfairly by peers were significantly associated with parents' cautions and warnings to children about intergroup relations (Promotion of Mistrust). Moreover, the influence of parents' perceptions on Promotion of Mistrust were especially pronounced when children also reported unfair treatment from adults. Children's identity exploration and unfair treatment were not associated with parents' emphasis on ethnic pride, heritage, and diversity (Cultural Socialization/Pluralism). Thus, findings suggest that parental factors are most central in the racial socialization messages that children receive. However, children's perceptions of discrimination and information seeking regarding their own history appear to have some influence on parental messages about race.     

Pilot–pivotal trials for average bioequivalence

Before carrying out a full scale bioequivalence trial, it is desirable to conduct a pilot trial to decide if a generic drug product shows promise of bioequivalence. The purpose of a pilot trial is to screen test formulations, and hence small sample sizes can be used. Based on the outcome of the pilot trial, one can decide whether or not a full scale pivotal trial should be carried out to assess bioequivalence. This article deals with the design of a pivotal trial, based on the evidence from the pilot trial. A two-stage adaptive procedure is developed in order to determine the sample size and the decision rule for the pivotal trial, for testing average bioequivalence using the two one-sided test (TOST). Numerical implementation of the procedure is discussed in detail, and the required tables are provided. Numerical results indicate that the required sample sizes could be smaller than that recommended by the FDA for a single trial, especially when the pilot study provides strong evidence in favor of bioequivalence.     

Conditional approval: discussion points from the PSI conditional approval expert group

The European Agency for the Evaluation of Medicinal Products has recently completed the consultation of a draft guidance on how to implement conditional approval. This route of application is available for orphan drugs, emergency situations and serious debilitating or life-threatening diseases. Although there has been limited experience in implementing conditional approval to date, PSI (Statisticians in the Pharmaceutical Industry) sponsored a meeting of pharmaceutical statisticians with an interest in the area to discuss potential issues. This article outlines the issues raised and resulting discussions, based on the group's interpretation of the legislation. Conditional approval seems to fit well with the accepted regulatory strategy in HIV. In oncology, conditional approval may be most likely when (a) compelling phase II data are available using accepted clinical outcomes (e.g. progression/recurrence-free survival or overall survival) and Phase III has been planned or started, or (b) when data are available using a surrogate endpoint for clinical outcome (e.g. response rate or biochemical measures) from a single-arm study in rare tumours with high response, compared with historical data. The use of interim analyses in Phase III for supporting conditional approval raises some challenging issues regarding dissemination of information, maintenance of blinding, potential introduction of bias, ethics, switching, etc.     

Using Private Social Care Services in Finland: Free or Forced Choices for Older People?

ABSTRACT

Use of private social care services among older people is increasing in Finland. This study aims to understand why older people choose private care in a comprehensive tax-subsidized social care system and examines whether people choose private service as a free choice or a forced choice as well as what factors contribute toward making these choices. Data for this study (N = 1,436) were gathered in 2010 from people aged 75 and above living independently at home in two Finnish cities: Tampere and Jyväskylä. Data were analyzed with several quantitative tests: chi-squared tests, multinomial regression analysis, and qualitative content analysis (for the open-ended responses from the survey questionnaire). Findings reveal that people chose private services mostly because of the effortlessness involved in its use and of the need for additional services that are unavailable through municipality; for example, cleaning. Majority of the respondents performed a free choice to use private services. People who lived in a city center with a higher level of income and who needed more services were more likely to be constrained toward using private support. Major concern, due to diminishing public service provision, is about service accessibility of economically disadvantaged groups; therefore, more research is required to understand the effects of the growing care market in Finland.     

Corporate Strategy Formulation and Taxation: Evidence from UK Firms*

This paper considers the relationship between corporate strategy formulation and taxation. Drawing on prior literature we briefly review the important influence that international taxation has on an array of corporate strategy decisions. We then consider issues in strategy formulation and taxation planning in order to develop an understanding of when and how taxation factors impinge on strategic decision‐making. We draw out the apparent paradox between the nature of strategic decision‐making and financial decision‐making and look for areas of reconciliation. In order to shed light on some of these issues we present findings from the qualitative analysis of a set of personal interviews undertaken with senior tax practitioners in seven UK‐based multinational enterprises and then consider quantitative responses from the tax practitioners working in 145 UK firms.