Analysis of growth curve data by using cubic smoothing splines

Longitudinal data frequently arises in various fields of applied sciences where individuals are measured according to some ordered variable, e.g. time. A common approach used to model such data is based on the mixed models for repeated measures. This model provides an eminently flexible approach to modeling of a wide range of mean and covariance structures. However, such models are forced into a rigidly defined class of mathematical formulas which may not be well supported by the data within the whole sequence of observations. A possible non-parametric alternative is a cubic smoothing spline, which is highly flexible and has useful smoothing properties. It can be shown that under normality assumption, the solution of the penalized log-likelihood equation is the cubic smoothing spline, and this solution can be further expressed as a solution of the linear mixed model. It is shown here how cubic smoothing splines can be easily used in the analysis of complete and balanced data. Analysis can be greatly simplified by using the unweighted estimator studied in the paper. It is shown that if the covariance structure of random errors belong to certain class of matrices, the unweighted estimator is the solution to the penalized log-likelihood function. This result is new in smoothing spline context and it is not only confined to growth curve settings. The connection to mixed models is used in developing a rough testing of group profiles. Numerical examples are presented to illustrate the techniques proposed.     

To live an ordinary life: resource needs and additional costs for people with a physical impairment

Disabled people face increased risks of living in poverty largely due to lower incomes and extra resource requirements compared to non-disabled people. This study incorporated the social model of disability with an economic approach to costing to estimate the additional costs required by people with a physical impairment to achieve an adequate standard of living in New Zealand. Budgets estimating the additional equipment, modifications, transport, support and time required to achieve an adequate standard of living were developed and validated through focus groups with community members. The findings suggest that reducing barriers involves substantial costs ranging from NZ$645–$2,348 per week.     

Measuring Social Return on Investment

Strategic decision making and evaluation in philanthropic giving and social investment requires good‐quality information about the social impacts of that investment. One way to meet this need is by calculating a social return on investment (SROI) measure, akin to the return on investment (ROI) approach used in business analysis. Despite much buzz in the field, SROI measurements are rarely used, in part because of the complexity of the calculations but also because of a number of thorny and often expensive organizational challenges associated with implementing an SROI process. This article explores these implementation challenges by comparing four social venture organizations in the health care field—two in the Netherlands and two in the United States—that have utilized some sort of SROI measurement. We summarize the SROI process and identify the specific organizational challenges in each case. Lessons learned from this analysis include the value of process versus product and the importance of fitting the type of measurement to the organizational context. We conclude with a summary of best practices for organizations and social investors who might try to make effective use of SROI measures.     

(Im)perishable Pleasure, (In)destructible Desire: Sexual Themes in U.S. and English News Coverage of Male Circumcision and Female Genital Cutting

Under what conditions do sexual pleasure and desire get addressed in news coverage of sexual health issues like female genital cutting (FGC) and male circumcision (MC)? In this study we employed an embodied ethnosexuality approach to analyze sexual themes in 1,902 items published from 1985 to 2009 in 13 U.S. and 8 English newspapers and news magazines. Journalists' discussions of sexual pleasure, desire, control, problems, and practices differed in quantity and quality depending on the practice and nation to which they pertained. News coverage in both nations presented FGC as impeding female sexual pleasure, desire, and activity in ways that reinforce (hetero)sexist understandings of sexuality. The English press depicted MC as diminishing male sexuality, whereas U.S. papers showed it as enhancing male sexuality. These patterns are influenced by, and serve to reinforce, cultural norms of embodiment and ethnosexual boundaries based on gender, race, and nationality. They may, in turn, shape public understandings of FGC and MC as social problems.     

ON THE INTERNAL REVENUE SERVICE'S SERVICE AND ENFORCEMENT

Built on the seminal work of Graetz et al. (1986), this study considers a model of tax compliance in which the Internal Revenue Service (IRS) services as well as audits taxpayers as in the real world. Taxpayers are uncertain about whether their incomes are eligible for deduction/exemption, and may seek advice from the taxpayer service provided by the IRS to mitigate the uncertainty. We show: (1) while the society's preferred quality of taxpayer service is likely to be sufficiently high, the IRS's preferred quality of taxpayer service is only at an intermediate level; and (2) the conflict between the society and the IRS tends to be intensified as the cost of tax audits becomes lower. Evidence in support of our results is addressed. We also extend our model to addressing the issue of corruption in tax administration and to considering a dynamic model. (JEL D82, H26, K42)     

The disagreeable behaviour of the kappa statistic

It is often of interest to measure the agreement between a number of raters when an outcome is nominal or ordinal. The kappa statistic is used as a measure of agreement. The statistic is highly sensitive to the distribution of the marginal totals and can produce unreliable results. Other statistics such as the proportion of concordance, maximum attainable kappa and prevalence and bias adjusted kappa should be considered to indicate how well the kappa statistic represents agreement in the data. Each kappa should be considered and interpreted based on the context of the data being analysed. Copyright © 2014 JohnWiley & Sons, Ltd.     

Hedging Barrier Options in GARCH Models with Transaction Costs

This study proposes a modified strike‐spread method for hedging barrier options in generalized autoregressive conditional heteroskedasticity (GARCH) models with transaction costs. A simulation study was conducted to investigate the hedging performance of the proposed method in comparison with several well‐known static methods for hedging barrier options. An accurate, easy‐to‐implement and fast scheme for generating the first passage time under the GARCH framework which enhances the accuracy and efficiency of the simulation is also proposed. Simulation results and an empirical study using real data indicate that the proposed approach has a promising performance for hedging barrier options in GARCH models when transaction costs are taken into consideration.