Moving college health research forward: Reconsidering our reliance on statistical significance testing

Understanding the unique health needs of college students and establishing best practices to address them depend, heavily, on the inherent quality and contribution of the research identifying these needs. College health-focused publications currently exemplify less than ideal statistical reporting practices. Specifically, college health practitioners and researchers continue to rely heavily upon null hypothesis significance testing (NHST) as the sole standard for effectiveness, validity, and/or replicability of scientific studies, even though NHST itself was not designed for such purposes. Herein we address the following questions: (a) What is NHST? (b) What are the inherent limitations of NHST? (c) What are recommended alternatives to NHST? and (d) How can editorial policies promote adopting NHST alternatives? Using college health data from the CORE 2011 Alcohol and Drug survey, we provide a heuristic example demonstrating how effect sizes do not suffer from the same limitations as NHST.     

Applying the Partitioned Multiobjective Risk Method (PMRM) to Portfolio Selection

The analysis of risk-return tradeoffs and their practical applications to portfolio analysis paved the way for Modern Portfolio Theory (MPT), which won Harry Markowitz a 1992 Nobel Prize in Economics. A typical approach in measuring a portfolio's expected return is based on the historical returns of the assets included in a portfolio. On the other hand, portfolio risk is usually measured using volatility, which is derived from the historical variance-covariance relationships among the portfolio assets. This article focuses on assessing portfolio risk, with emphasis on extreme risks. To date, volatility is a major measure of risk owing to its simplicity and validity for relatively small asset price fluctuations. Volatility is a justified measure for stable market performance, but it is weak in addressing portfolio risk under aberrant market fluctuations. Extreme market crashes such as that on October 19, 1987 ("Black Monday") and catastrophic events such as the terrorist attack of September 11, 2001 that led to a four-day suspension of trading on the New York Stock Exchange (NYSE) are a few examples where measuring risk via volatility can lead to inaccurate predictions. Thus, there is a need for a more robust metric of risk. By invoking the principles of the extreme-risk-analysis method through the partitioned multiobjective risk method (PMRM), this article contributes to the modeling of extreme risks in portfolio performance. A measure of an extreme portfolio risk, denoted by f(4), is defined as the conditional expectation for a lower-tail region of the distribution of the possible portfolio returns. This article presents a multiobjective problem formulation consisting of optimizing expected return and f(4), whose solution is determined using Evolver-a software that implements a genetic algorithm. Under business-as-usual market scenarios, the results of the proposed PMRM portfolio selection model are found to be compatible with those of the volatility-based model. However, under extremely unfavorable market conditions, results indicate that f(4) can be a more valid measure of risk than volatility.     

Measuring Quality of Life in Small Areas Over Different Periods of Time

The purpose of this paper is todescribe an index methodology for measuringquality of life, understood multidimensionally,in a set of very different municipalities,units of measurement, and time periods.Although certain technical problems arise whensmall areas (municipalities) are considered,cross and serial comparison is completed. Themethodology was applied in 314 municipalitiesof the province of Barcelona (Spain).     

Relationships with Citizens in Public Management: A Study at the Largest Spanish Town Halls

This paper provides an analysis of the relationships existing between citizen participation and satisfaction levels within the framework of Spanish local administrations, additionally paying attention to the links between organisational size and the said participation and satisfaction levels. The results of a survey questionnaire answered by 388 Human Resources (HR) managers from the largest Spanish Town Halls were examined for these purposes. A claim is made both to increase the degree of citizen participation in public decision-making and to ensure the delivery of efficient and effective public services that can really meet citizens’ needs in Spanish town Halls.     

Aftershocks of Chile's earthquake for an ongoing, large-scale experimental evaluation

Evaluation designs for social programs are developed assuming minimal or no disruption from external shocks, such as natural disasters. This is because extremely rare shocks may not make it worthwhile to account for them in the design. Among extreme shocks is the 2010 Chile earthquake. Un Buen Comienzo (UBC), an ongoing early childhood program in Chile, was directly affected by the earthquake. This article discusses (a) the factors the UBC team considered for deciding whether to put on hold or continue implementation and data collection for this experimental study; and (b) how the team reached consensus on those decisions. A lesson learned is that the use of an experimental design for UBC insured that the evaluation's internal validity was not compromised by the earthquake's consequences, although cohort comparisons were compromised. Other lessons can be transferred to other contexts where external shocks affect an ongoing experimental or quasi-experimental impact evaluation.     

Effect of autocorrelation when estimating the trend of a time series via penalized least squares with controlled smoothness

This paper studies the effect of autocorrelation on the smoothness of the trend of a univariate time series estimated by means of penalized least squares. An index of smoothness is deduced for the case of a time series represented by a signal-plus-noise model, where the noise follows an autoregressive process of order one. This index is useful for measuring the distortion of the amount of smoothness by incorporating the effect of autocorrelation. Different autocorrelation values are used to appreciate the numerical effect on smoothness for estimated trends of time series with different sample sizes. For comparative purposes, several graphs of two simulated time series are presented, where the estimated trend is compared with and without autocorrelation in the noise. Some findings are as follows, on the one hand, when the autocorrelation is negative (no matter how large) or positive but small, the estimated trend gets very close to the true trend. Even in this case, the estimation is improved by fixing the index of smoothness according to the sample size. On the other hand, when the autocorrelation is positive and large the simulated and estimated trends lie far away from the true trend. This situation is mitigated by fixing an appropriate index of smoothness for the estimated trend in accordance to the sample size at hand. Finally, an empirical example serves to illustrate the use of the smoothness index when estimating the trend of Mexico’s quarterly GDP.     

Genetic variants in ATP6 and ND3 mitochondrial genes are not associated with aggressive prostate cancer in Mexican–Mestizo men with overweight or obesity

Mitochondrial defects have been related to obesity and prostate cancer. We investigated if Mexican–Mestizo men presenting this type of cancer, exhibited somatic mutations of ATP6 and/or ND3.Body mass index (BMI) was determined; the degree of prostate cancer aggressiveness was demarcated by the Gleason score. DNA from tumor tissue and from blood leukocytes was amplified by the polymerase chain reaction and ATP6 and ND3 were sequenced. We included 77 men: 20 had normal BMI, 38 were overweight and 19 had obesity; ages ranged from 52 to 83. After sequencing ATP6 and ND3, from DNA obtained from leukocytes and tumor tissue, we did not find any somatic mutations. All changes observed, in both genes, were polymorphisms. In ATP6 we identified, in six patients, two non-synonymous nucleotide changes and in ND3 we observed that twelve patients presented non-synonymous polymorphisms. To our knowledge, this constitutes the first report where the complete sequences of the ATP6 and ND3 have been analyzed in Mexican–Mestizo men with prostate cancer and diverse BMI. Our results differ with those reported in Caucasian populations, possibly due to ethnic differences.     

"MEN I MESS WITH DON'T HAVE ANYTHING TO DO WITH AIDS":

Pivotal in HIV/STD intervention and prevention is how individuals perceive risk. This article discusses how ethnotheory can be used to understand the underpinnings of risk perception from the subject's perspective. Ethnotheory's theoretical and methodological character extends present models used to explain sex-related HIV behaviors and provides insights into risk perception useful for the development of effective intervention strategies. Four detailed ethnographic excerpts from low-income African American and Mexican American men and women illustrate how people form perceptions of risk and how information gained through ethnotheory is useful in the design of culturally relevant interventions.     

Generalized modified slash distribution with applications

Abstract

In this article a generalization of the modified slash distribution is introduced. This model is based on the quotient of two independent random variables, whose distributions are a normal and a one-parameter gamma, respectively. The resulting distribution is a new model whose kurtosis is greater than other slash distributions. The probability density function, its properties, moments, and kurtosis coefficient are obtained. Inference based on moment and maximum likelihood methods is carried out. The multivariate version is also introduced. Two real data sets are considered in which it is shown that the new model fits better to symmetric data with heavy tails than other slash extensions previously introduced in literature.