The EPQ with partial backordering and phase-dependent backordering rate

In previous work we established a closed-form optimal stocking strategy for an EPQ model with partial backordering at a constant rate β. Here we extend this work to allow for the possibility that the percentage of demand backordered will increase when production starts again. We show how our previous model can be adapted to find the optimal decision variable values for this new assumption and develop the condition that the initial value of β must meet for partial backordering to be optimal.     

Spectral estimation for locally stationary time series with missing observations

Time series arising in practice often have an inherently irregular sampling structure or missing values, that can arise for example due to a faulty measuring device or complex time-dependent nature. Spectral decomposition of time series is a traditionally useful tool for data variability analysis. However, existing methods for spectral estimation often assume a regularly-sampled time series, or require modifications to cope with irregular or ‘gappy’ data. Additionally, many techniques also assume that the time series are stationary, which in the majority of cases is demonstrably not appropriate. This article addresses the topic of spectral estimation of a non-stationary time series sampled with missing data. The time series is modelled as a locally stationary wavelet process in the sense introduced by Nason et al. (J. R. Stat. Soc. B 62(2):271–292, 2000) and its realization is assumed to feature missing observations. Our work proposes an estimator (the periodogram) for the process wavelet spectrum, which copes with the missing data whilst relaxing the strong assumption of stationarity. At the centre of our construction are second generation wavelets built by means of the lifting scheme (Sweldens, Wavelet Applications in Signal and Image Processing III, Proc. SPIE, vol. 2569, pp. 68–79, 1995), designed to cope with irregular data. We investigate the theoretical properties of our proposed periodogram, and show that it can be smoothed to produce a bias-corrected spectral estimate by adopting a penalized least squares criterion. We demonstrate our method with real data and simulated examples.     

Bayesian inference for pairwise interacting point processes

Pairwise interacting point processes are commonly used to model spatial point patterns. To perform inference, the established frequentist methods can produce good point estimates when the interaction in the data is moderate, but some methods may produce severely biased estimates when the interaction in strong. Furthermore, because the sampling distributions of the estimates are unclear, interval estimates are typically obtained by parametric bootstrap methods. In the current setting however, the behavior of such estimates is not well understood. In this article we propose Bayesian methods for obtaining inferences in pairwise interacting point processes. The requisite application of Markov chain Monte Carlo (MCMC) techniques is complicated by an intractable function of the parameters in the likelihood. The acceptance probability in a Metropolis-Hastings algorithm involves the ratio of two likelihoods evaluated at differing parameter values. The intractable functions do not cancel, and hence an intractable ratio r must be estimated within each iteration of a Metropolis-Hastings sampler. We propose the use of importance sampling techniques within MCMC to address this problem. While r may be estimated by other methods, these, in general, are not readily applied in a Bayesian setting. We demonstrate the validity of our importance sampling approach with a small simulation study. Finally, we analyze the Swedish pine sapling dataset (Strand 1972) and contrast the results with those in the literature.     

Regional Religions?: Extending the “Semi-involuntary” Thesis of African-American Religious Participation

This research examines religious affiliation and church attendance among African-Americans in three different regions of the United States to evaluate the thesis that the Black church represents a semi-involuntary institution shaped by historical dynamics of segregation in the rural South. We extend the analyses of others who have found the rural South to have distinctive church participation patterns by examining two nationally representative data sets (the 1972–1996 General Social Surveys and the 1984 National Alcohol Study). We explore both level and type of church attendance of African-Americans, and how patterns differ by region. Further, we refine prior analyses by (1) differentiating between members of historically White and conservative churches from those in the black mainline, (2) examining racial segregation, and (3) focusing on the type of church attendance (rather than just overall level). Ordinary Least Squares (OLS) and logistic regression models support the thesis that the rural South exhibits some distinctive patterns that make the semi-involuntary institution notion a useful concept, although patterns not predicted by the thesis are also found. The semi-involuntary thesis is also used to illuminate some church attendance patterns observed outside the rural South.     

Willingness to speak out about gay laws reform: some cause for optimism

We examined the extent to which people's private attitudes to gay law reform are influenced by the attitudes of others. Ninety-six university students were told that they were either in a minority or in a majority relative to their university group on their attitudes to gay law reform. Contrary to a number of assumptions made in the social psychological literature, participants who supported gay law reform were more prepared to act in line with their attitudes than were those who opposed gay law reform. Furthermore, anti-gay law reform participants appeared to reassess their attitudes when they were told they were in a minority; in contrast, pro-gay law reform participants were unaffected by the group norm. This suggests that anti-gay law reform attitudes are softer and more easily influenced than are pro-gay law reform attitudes. The implications of these results for activists are discussed.     

Ethics in behavioral genetics research

As research in behavioral genetics uncovers the genetic contribution to human behavior, it will undoubtedly further our understanding of normal human variation in many behavioral traits, such as personality, intelligence, and sexuality. This research also shows great potential for the diagnosis, treatment, and prevention of mental illnesses. Recent findings underscore this potential and document the increasing validity of research methods--methods that in the past have led to mistaken inferences about genes "for" violent behavior and homosexuality. Although all research with human subjects requires adequate attention to its ethical aspects, certain ethical issues involved with behavioral genetics are particularly acute and deserve careful attention. This article reviews these selected major ethical issues arising in (1) the conduct of behavioral genetics research; and (2) the application of its research findings. While some of the ethical concerns in the latter category are likely to be of substantial importance and animate considerable popular concern, they currently fall outside the realm of traditional research review. Determining how to deal with these concerns should be a focus of future scholarly work.     

Reports of childhood sexual abuse by adolescents and young adults: stability over time

The consistency of childhood sexual abuse (CSA) reporting was explored in this study. Two-hundred seventeen adolescents and young adults (ages 14-24) enrolled in urban health care clinics completed self-report questionnaires assessing CSA and other problem behaviors at enrollment and at 7 months. Results indicated that the stability of CSA self-report at two time points was poor (58% consistent nonreporters of CSA, 20% consistent reporters, 22% inconsistent reporters). Consistent and inconsistent reporters were differentiated on risk measures. Adolescents who endorsed more items from the CSA scale were five times more likely to be consistent reporters. In sum, adolescent CSA reporting was quite inconsistent over time. Using multi-item scales and assessing CSA at two time points enhances accuracy of reporting.     

Guns and gun threats at college

A random sample of more than 10,000 undergraduate students, selected from 119 4-year colleges, answered a mailed questionnaire about gun possession and gun threats. Approximately 4.3% of the students reported that they had a working firearm at college, and 1.6% of them have been threatened with a gun while at school. Students are more likely to have a firearm at college and to be threatened with a gun while at college if they are male, live off campus, binge drink, engage in risky and aggressive behavior after drinking, and attend institutions in regions of the United States where household firearm prevalence is high. Having a firearm for protection is also strongly associated with being threatened with a gun while at college. Students who reported having firearms at college disproportionately reported that they engaged in behaviors that put themselves and others at risk for injury.