Combining forecast quantiles using quantile regression: Investigating the derived weights, estimator bias and imposing constraints

SUMMARY A novel proposal for combining forecast distributions is to use quantile regression to combine quantile estimates. We consider the usefulness of the resultant linear combining weights. If the quantile estimates are unbiased, then there is strong intuitive appeal for omitting the constant and constraining the weights to sum to unity in the quantile regression. However, we show that suppressing the constant renders one of the main attractive features of quantile regression invalid. We establish necessary and sufficient conditions for unbiasedness of a quantile estimate, and show that a combination with zero constant and weights that sum to unity is not necessarily unbiased.     

Discerning the epidemiology of drug use among a sample of college students

Although estimates concerning the prevalence of various forms of substance abuse vary considerably, it is critical to note that even the more conservative estimates indicate a major public health problem. Furthermore, increased drug experimentation has been frequently associated with the college experience. Utilizing a slightly modified version of the National Institute on Drug Abuse (NIDA) Monitoring the Future Survey, the present study examined the epidemiology of self-reported drug taking behaviors (e.g., alcohol, marijuana, tranquilizers, stimulants, psychedelics, etc.) among a sample (n = 683) of students attending a major public university. Data analyses focused on the specific settings and social groupings in which drug use occurred as well as on the frequency and type(s) of drug taking behaviors. Based on the results yielded from a disjoint cluster analysis, four distinct groups of drug users were identified. These four groups then served as categories of the dependent variable in a discriminant function analysis. A general linear models procedure was employed to identify the more efficacious discriminating (i.e., independent) variables.     

Smoothing parameter selection in nonparametric regression using an improved Akaike information criterion

Many different methods have been proposed to construct nonparametric estimates of a smooth regression function, including local polynomial, (convolution) kernel and smoothing spline estimators. Each of these estimators uses a smoothing parameter to control the amount of smoothing performed on a given data set. In this paper an improved version of a criterion based on the Akaike information criterion (AIC), termed AIC_C, is derived and examined as a way to choose the smoothing parameter. Unlike plug-in methods, AIC_C can be used to choose smoothing parameters for any linear smoother, including local quadratic and smoothing spline estimators. The use of AIC_C avoids the large variability and tendency to undersmooth (compared with the actual minimizer of average squared error) seen when other 'classical' approaches (such as generalized cross-validation (GCV) or the AIC) are used to choose the smoothing parameter. Monte Carlo simulations demonstrate that the AIC_C-based smoothing parameter is competitive with a plug-in method (assuming that one exists) when the plug-in method works well but also performs well when the plug-in approach fails or is unavailable.     

Gender,Contraceptive Attitudes,and Condom Use in Adolescent Romantic Relationships: A Dyadic Approach

Although sexual risk behavior occurs in a dyadic context, most studies of adolescent sexual behavior focus on individuals. This study uses couple data (N = 488 couples) from the National Longitudinal Study of Adolescent Health to examine how partners' contraceptive attitudes correlate over time and whether male or female partners' attitudes are better predictors of condom use. Net of their own prior attitudes, partners' prior attitudes predicted both male and female adolescents' Wave 2 attitudes. This association was stronger for female than for male adolescents, suggesting that female attitudes were influenced more by males' prior attitudes than vice versa. When entered together, only male adolescents' attitudes predicted dyadic condom use. Findings suggest that male partners may have greater influence on adolescent contraceptive decisions and that prevention programs should emphasize the relational context of sexual behavior.     

The Challenges in Developing an Online Applied Statistics Program: Lessons Learned at Penn State University

Numerous professional fields have an increasing need for individuals trained in statistics and other quantitative analysis techniques. Today there exists great potential to fulfill this need by providing opportunities through online learning. However, to provide a high-quality education for returning adult professionals seeking advanced degrees in applied statistics online, many challenges need to be overcome. Based on our experience developing Penn State University’s online program in applied statistics, we discuss the evolution of the program’s curriculum, recruitment and development of online faculty, and meeting the requirements of students as important areas that require consideration in the development of an online program. We also highlight program evaluation strategies employed to ensure innovation and improvement in online education as cornerstones to a program’s success.     

Women’s Off-Farm Work Participation and Son Preference in Rural China

Population Research and Policy Review - China is a rapidly growing country, where a considerable amount of rural female labor has shifted from agricultural to nonagricultural sectors. Meanwhile, a...     

Local Authorities Unemployment Strategies

If a "co-ordinated strategy to reduce the major problem of unemployment" is needed, as Leaper claimed in previous volume, there remains the question of how to develop such a strategy. Central governmental agencies like the MSC have major programmes, but other consequences of high unemployment have to be dealt with by local authorities. Four case studies of attempts made by local authorities in this regard are then examined. The most prominent features in their strategies are: information giving, training provision, job creation and channelling funding from other agencies or internal co-ordinated funding. The new strategies have involved changes in management and liaison, in policy review and affirmation.     

Old People Living Alone—Is Organized Observation Necessary?

A survey of 192 old people was carried out to assess the need for a paid daily visitor as a means of ensuring prompt help in cases of illness or accident. The survey found evidence of a comprehensive network of care from neighbours for the elderly people living near them. Neighbour observation and support made a daily Street Visitor Scheme superfluous.     

Process and Results of an Immunization Requirement at the University of Rochester

Abstract

“A Double-Blind Study of Oral Acyclovir for Suppression of Recurrences of Genital Herpes Simplex Virus Infection,” JOHN M. DOUGLAS, et al. Patients with frequently recurring genital herpes were enrolled in a double-blind placebo-controlled trial comparing 200-mg acyclovir capsules, given five or two times daily, with placebo. Of 47 placebo recipients, 44 (94 per cent) had recurrences during the 120-day treatment period, compared with 13 (29 per cent) of 45 patients treated with acyclovir five times daily and 18 of 51 (35 per cent) treated with acyclovir twice daily (P < 0.001 for each regimen compared with placebo). The median time to the first clincial recurrence was 18 days in placebo recipients, compared with over 120 days in both acyclovir-treated groups (P < 0.001 for both groups compared with placebo). The mean monthly recurrence rate during the medication period was 0.86 in placebo recipients, compared with 0.13 in patients treated with acyclovir five times daily and 0.14 in patients treated with acyclovir twice daily (P < 0.001 for both groups compared with placebo). While receiving therapy, 86 of 96 acyclovir-treated patients had over a 50 per cent reduction in their pretreatment recurrence rate. Breakthrough recurrences in acyclovir recipients were of shorter duration and associated with a lower frequency of viral shedding than recurrences in placebo recipients. After medication was discontinued, the subsequent recurrence rate returned to pretreatment frequencies. Daily oral acyclovir was well tolerated. We conclude that oral acyclovir given for four months markedly reduces but does not completely prevent recurrences of genital herpes and does not influence the long-term natural history of the disease. (New England Journal of Medicine 1984 July;310:1551–6.)