Sequential design approaches for bioequivalence studies with crossover designs

The planning of bioequivalence (BE) studies, as for any clinical trial, requires a priori specification of an effect size for the determination of power and an assumption about the variance. The specified effect size may be overly optimistic, leading to an underpowered study. The assumed variance can be either too small or too large, leading, respectively, to studies that are underpowered or overly large. There has been much work in the clinical trials field on various types of sequential designs that include sample size reestimation after the trial is started, but these have seen only little use in BE studies. The purpose of this work was to validate at least one such method for crossover design BE studies. Specifically, we considered sample size reestimation for a two-stage trial based on the variance estimated from the first stage. We identified two methods based on Pocock's method for group sequential trials that met our requirement for at most negligible increase in type I error rate.     

Bootstrap goodness-of-fit test for the beta-binomial model

A common question in the analysis of binary data is how to deal with overdispersion. One widely advocated sampling distribution for overdispersed binary data is the beta-binomial model. For example, this distribution is often used to model litter effects in toxicological experiments. Testing the null hypothesis of a beta-binomial distribution against all other distributions is difficult, however, when the litter sizes vary greatly. Herein, we propose a test statistic based on combining Pearson statistics from individual litter sizes, and estimate the p-value using bootstrap techniques. A Monte Carlo study confirms the accuracy and power of the test against a beta-binomial distribution contaminated with a few outliers. The method is applied to data from environmental toxicity studies.     

Market management of the essential economy: an essay

This essay presents a framework for thinking about public economic policy. The argument is that the prevailing theory of competitive markets serves a useful public purpose but creates problems when made into an ideology. The core theory and philosophy suffers from oversights and illusions. Fundamentalist thinking found in it can be dangerous for the long run well-being of humanity. These insights lead to the conclusion that the fundamental task of an economics for public policy should be to develop a theory of workable markets.     

Educational attainment and employment of young adults ageing out of care: A registry study based on the Finnish birth cohort 1987

Adolescents growing up outside their birth homes are at major risk for multiple adversities in early adulthood, including low education and unemployment. The transition from out-of-home placement to independent living overlaps with the transition from school to work and higher education. However, the support during this critical phase is often inadequate. Adolescents ageing out of care are also more likely to have faced adversities in their birth families. Yet, the interplay between different risk factors and having aged out of care has gained little attention. This study aimed to assess known risk factors for low education and unstable employment and their interaction with ageing out of care, controlling for birth-home-related adversities. We assessed this topic using logistic and linear regression modelling based on the Finnish birth cohort 1987 (n = 59 476) registry. Our analysis showed that obtaining upper secondary and higher education was much less likely among those ageing out of care, and they had spent 52–80 fewer days annually in employment after graduation. Few interactions with other risk factors were, however, found. Efforts are needed to prevent inequalities in education and employment for those ageing out of care in the transition phase from school to work.     

Conditional Correlation Models of Autoregressive Conditional Heteroscedasticity With Nonstationary GARCH Equations

In this article, we investigate the effects of careful modeling the long-run dynamics of the volatilities of stock market returns on the conditional correlation structure. To this end, we allow the individual unconditional variances in conditional correlation generalized autoregressive conditional heteroscedasticity (CC-GARCH) models to change smoothly over time by incorporating a nonstationary component in the variance equations such as the spline-GARCH model and the time-varying (TV)-GARCH model. The variance equations combine the long-run and the short-run dynamic behavior of the volatilities. The structure of the conditional correlation matrix is assumed to be either time independent or to vary over time. We apply our model to pairs of seven daily stock returns belonging to the S&P 500 composite index and traded at the New York Stock Exchange. The results suggest that accounting for deterministic changes in the unconditional variances improves the fit of the multivariate CC-GARCH models to the data. The effect of careful specification of the variance equations on the estimated correlations is variable: in some cases rather small, in others more discernible. We also show empirically that the CC-GARCH models with time-varying unconditional variances using the TV-GARCH model outperform the other models under study in terms of out-of-sample forecasting performance. In addition, we find that portfolio volatility-timing strategies based on time-varying unconditional variances often outperform the unmodeled long-run variances strategy out-of-sample. As a by-product, we generalize news impact surfaces to the situation in which both the GARCH equations and the conditional correlations contain a deterministic component that is a function of time.     

Transformational leadership climate: Performance linkages, mechanisms, and boundary conditions at the organizational level

Transformational leadership (TFL) climate describes the degree to which leaders throughout an organization engage in TFL behaviors. In this study, we investigate performance linkages, mechanisms, and boundary conditions of TFL climate at the organizational level of analysis. In a sample of 158 independent organizations, 18,094 employees provided data on TFL climate, positive affective climate, trust climate, and employees' task performance behavior and organizational citizenship behavior. In addition, human resource managers rated overall employee productivity. Study results yielded a pattern of moderated mediation for overall employee productivity and employees' aggregate task performance behavior, in that an organization's TFL climate was indirectly (through positive affective climate) related with these outcome variables under conditions of high trust climate, but not under conditions of low trust climate. Further, we found an organization's TFL climate to indirectly relate with employees' aggregate organizational citizenship behavior through positive affective climate, largely independent of the level of trust climate.     

Does the internet change how we die and mourn? Overview and analysis

The article outlines the issues that the internet presents to death studies. Part 1 describes a range of online practices that may affect dying, the funeral, grief and memorialization, inheritance and archaeology; it also summarizes the kinds of research that have been done in these fields. Part 2 argues that these new online practices have implications for, and may be illuminated by, key concepts in death studies: the sequestration (or separation from everyday life) of death and dying, disenfranchisement of grief, private grief, social death, illness and grief narratives, continuing bonds with the dead, and the presence of the dead in society. In particular, social network sites can bring dying and grieving out of both the private and public realms and into the everyday life of social networks beyond the immediate family, and provide an audience for once private communications with the dead.     

Duality of weakly disposable technology

The axiom of weak disposability is frequently imposed in data envelopment analysis (DEA) models involving undesirable outputs such as pollution. This paper sheds new light on the economic interpretation of weak disposability by developing dual formulations of the weakly disposable DEA technology. We find that the economic implications of weak disposability on the multiplier DEA problem are two-fold: (1) the shadow prices of the undesirable outputs can be positive or negative, and (2) the economic loss of the benchmark cannot exceed the suck cost of the inputs. We interpret the second implications as a limited liability condition. The dual formulations developed in this paper enable one to estimate shadow prices of the undesirable outputs using the weakly disposable technology. The insights gained are illustrated by a numerical example and an empirical application to the US power plants.     

Multi-horizon Markowitz portfolio performance appraisals: A general approach

This article extends the analysis of multi-horizon mean-variance portfolio analysis in the Morey and Morey [Mutual fund performance appraisals: a multi-horizon perspective with endogenous benchmarking. Omega 1999;27:241–58] article in several ways. First, instead of either proportionally contracting risk dimensions or proportionally expanding return dimensions, a more general efficiency measure simultaneously attempts to reduce risk and to expand return over all time periods. Second, a duality relation is established between this generalized multi-horizon efficiency measure and an indirect mean-variance utility function, underscoring the natural interpretation of this generalized efficiency measure in terms of investor's preferences. Furthermore, the need to properly apply time discounting in multi-horizon mean-variance portfolio problems is argued for. An empirical illustration based on the original mutual fund data set in Morey and Morey [Mutual fund performance appraisals: a multi-horizon perspective with endogenous benchmarking. Omega 1999;27:241–58] is added to contrast the new and the original approaches.