THE INTERNAL AND EXTERNAL VALIDITY OF THE REGRESSION DISCONTINUITY DESIGN: A META‐ANALYSIS OF 15 WITHIN‐STUDY COMPARISONS

Theory predicts that regression discontinuity (RD) provides valid causal inference at the cutoff score that determines treatment assignment. One purpose of this paper is to test RD's internal validity across 15 studies. Each of them assesses the correspondence between causal estimates from an RD study and a randomized control trial (RCT) when the estimates are made at the same cutoff point where they should not differ asymptotically. However, statistical error, imperfect design implementation, and a plethora of different possible analysis options, mean that they might nonetheless differ. We test whether they do, assuming that the bias potential is greater with RDs than RCTs. A second purpose of this paper is to investigate the external validity of RD by exploring how the size of the bias estimates varies across the 15 studies, for they differ in their settings, interventions, analyses, and implementation details. Both Bayesian and frequentist meta‐analysis methods show that the RD bias is below 0.01 standard deviations on average, indicating RD's high internal validity. When the study‐specific estimates are shrunken to capitalize on the information the other studies provide, all the RD causal estimates fall within 0.07 standard deviations of their RCT counterparts, now indicating high external validity. With unshrunken estimates, the mean RD bias is still essentially zero, but the distribution of RD bias estimates is less tight, especially with smaller samples and when parametric RD analyses are used.     

“An Inherited Money Dude from Queens County”: How Unseen Candidate Characteristics Affect Voter Perceptions

Political Behavior - We examine the effect of biographical knowledge on voters’ assessments of leaders. Prior research has shown that voters infer traits from candidate characteristics such...     

Generating a Corpus of Mobile Forensic Images for Masquerading user Experimentation

The Periodic Mobile Forensics (PMF) system investigates user behavior on mobile devices. It applies forensic techniques to an enterprise mobile infrastructure, utilizing an on‐device agent named TractorBeam. The agent collects changed storage locations for later acquisition, reconstruction, and analysis. TractorBeam provides its data to an enterprise infrastructure that consists of a cloud‐based queuing service, relational database, and analytical framework for running forensic processes. During a 3‐month experiment with Purdue University, TractorBeam was utilized in a simulated operational setting across 34 users to evaluate techniques to identify masquerading users (i.e., users other than the intended device user). The research team surmises that all masqueraders are undesirable to an enterprise, even when a masquerader lacks malicious intent. The PMF system reconstructed 821 forensic images, extracted one million audit events, and accurately detected masqueraders. Evaluation revealed that developed methods reduced storage requirements 50‐fold. This paper describes the PMF architecture, performance of TractorBeam throughout the protocol, and results of the masquerading user analysis.     

Troubling notions of farmer choice: hybrid Bt cotton seed production in western India

The debate over agricultural biotechnology is increasingly being centered on the question of farmer choice. Advocates for biotechnology argue that farmers should be able to choose the seeds and technologies they use, and therefore these new technologies should be legalized and made available immediately. Who would deny farmers of the global South their right to choose? But these discourses of choice and freedom are being deployed to market a particular kind of development. This neoliberal development of agriculture is leading to the individualization of risk, the shifting of risk to marginalized contract farming households, and greater control for wealthier farmers, seed companies and agents. The state of Gujarat, India, is seen as a success story of hybrid Bt cotton, in which farmers have their choice of hundreds of varieties of seeds. As cotton seed production is taking off in the neighboring state of Rajasthan, however, choosing Bt cotton has different implications and meanings altogether. Drawing on eight months of qualitative research with adivasi households in Dungarpur District, Rajasthan, I offer narrative accounts from farmers and seed agents that both explore and trouble neoliberal notions of farmer choice. The use of these discourses by biotech advocates is just one example of the ways that choice and freedom are being utilized to further neoliberal development.     

The influence of site of collection on postmortem morphine concentrations in heroin overdose victims

When assaying for postmortem morphine concentration, significant site sampling variability exists between central and peripheral sampling sites and even within sampling regions of the body. To study the variation, 76 suspected heroin overdoses were identified. Each had femoral artery (FA) and vein (FV), left and right ventricle and pooled heart blood samples obtained at autopsy. Forty-four tested positive for morphine. Morphine concentrations were determined by gas chromatography/mass spectrometry, with sampling site differences reported as log-transformed ratios and compared by signed rank test.The mean FA to FV ratio for total morphine was 1.2 (range 0-4.5). The ratio for left heart to right heart total morphine was 1.1 (range 0.4-3.2). Left ventricular to FV total morphine ratio was 2.0 (range 0.6-6.9). In these opioid overdose deaths, FA and FV morphine concentrations are usually similar, although up to 4.5-fold differences were noted. Centrally obtained morphine concentrations are on average twice as high compared with peripheral morphine concentrations. Left and right ventricular morphine concentrations were usually similar, although up to 3.2-fold differences were noted (left side higher).