On Tiku's robust procedure — a Bayesian insight

Tiku's robust procedure for testing mean and variance from nonnormal universe is examined from the Bayesian viewpoint. The posterior distribution of the scale parameter is derived and then approximated by a Laguerre polynomial expansion while the posterior distribution of the location parameter is approximated by a linear combination of t-distributions. For the example with Darwin's data, the approximations appear to be extremely good.     

Graduate Training and Initial Job Placement*

This study examines the extent to which professional credentials accrued during graduate school are related to postgraduate employment. The undergraduate and graduate records, demographic characteristics, and initial job placements of 711 Ph.D. recipients from the University of California, Santa Barbara, are analyzed. We find that several aspects of graduate training (e.g., holding research assistantships) have greater influence on the initial placement of women than men. Further, coauthored publications with the mentor influence the initial placement of men and women somewhat differently. Given the importance of initial placement in determining career productivity (e.g., Long and McGinnis, 1981; Reskin, 1978). these differences may have considerable impact on professional life chances.     

On drift parameter estimation in models with fractional Brownian motion

We consider a stochastic differential equation involving standard and fractional Brownian motion with unknown drift parameter to be estimated. We investigate the standard maximum likelihood estimate of the drift parameter, two non-standard estimates and three estimates for the sequential estimation. Model strong consistency and some other properties are proved. The linear model and Ornstein–Uhlenbeck model are studied in detail. As an auxiliary result, an asymptotic behaviour of the fractional derivative of the fractional Brownian motion is established.     

Threshold‐free estimation of functional antibody titers of a group B streptococcus opsonophagocytic killing assay

Opsonophagocytic killing assays (OPKA) are routinely used for the quantification of bactericidal antibodies in blood serum samples. Quantification of the OPKA readout, the titer, provides the basis for the statistical analysis of vaccine clinical trials having functional immune response endpoints. Traditional OPKA titers are defined as the maximum serum dilution yielding a predefined bacterial killing threshold value, and they are estimated by fitting a dose‐response model to the dilution‐killing curve. This paper illustrates a novel definition of titer, the threshold‐free titer, which preserves biological interpretability while not depending on any killing threshold or on a postulated shape of the dose‐response curve. These titers are shown to be more precise than the traditional threshold‐based titers when using simulated and experimental group B streptococcus OPKA experimental data. Also, titer linearity is shown to be not measurable when using threshold‐based titers, whereas it becomes measurable using threshold‐free titers. The biological interpretability and operational characteristics demonstrated here indicate that threshold‐free titers are an appropriate tool for the routine analysis of OPKA data. Copyright © 2015 John Wiley & Sons, Ltd.     

Supplementing a survey with respondent Twitter data to measure e-cigarette information exposure

ABSTRACT

Social media data are increasingly used by researchers to gain insights on individuals’ behaviors and opinions. Platforms like Twitter provide access to individuals’ postings, networks of friends and followers, and the content to which they are exposed. This article presents the methods and results of an exploratory study to supplement survey data with respondents’ Twitter postings, networks of Twitter friends and followers, and information to which they were exposed about e-cigarettes. Twitter use is important to consider in e-cigarette research and other topics influenced by online information sharing and exposure. Further, Twitter metadata provide direct measures of user’s friends and followers as opposed to survey self-reports. We find that Twitter metadata provide similar information to survey questions on Twitter network size without inducing recall error or other measurement issues. Using sentiment coding and machine learning methods, we find Twitter can elucidate on topics difficult to measure via surveys such as online expressed opinions and network composition. We present and discuss models predicting whether respondents’ tweet positively about e-cigarettes using survey and Twitter data, finding the combined data to provide broader measures than either source alone.     

Inequality in Volunteering: Building a New Research Front

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Volunteering research focuses predominantly on predicting participation in volunteering, proceeding from the...     

Does Perceived Social Support Buffer the Negative Effects of Type C Personality on Quality of Life of Breast Cancer Patients?

The present study investigated possible Type C personality–quality of life (QOL) relationship, and the moderating role of perceived social support in this relation among 101 postoperative breast cancer patients. Participants were from different cities in Turkey but receiving treatment in the capital, Ankara. Obtained data were analyzed by moderated regression analysis. According to the results, Type C personality was not related to the QOL of participants, however, higher perceived social support was associated with better QOL in patients. Also, perceived social support moderated Type C personality–QOL relation. Accordingly, patients high on Type C personality and perceived social support had the highest QOL. In contrast, patients high on Type C personality and low on perceived social support had the lowest QOL. Findings, as well as the strengths and limitations of the study, were discussed in the light of the relevant literature. As a possible clinical implication, enhancement of social support networks of the patients were suggested.