Detecting Spillover Effects: Design and Analysis of Multilevel Experiments

Interpersonal communication presents a methodological challenge and a research opportunity for researchers involved in field experiments. The challenge is that communication among subjects blurs the line between treatment and control conditions. When treatment effects are transmitted from subject to subject, the stable unit treatment value assumption (SUTVA) is violated, and comparison of treatment and control outcomes may provide a biased assessment of the treatment’s causal influence. Social scientists are increasingly interested in the substantive phenomena that lead to SUTVA violations, such as communication in advance of an election. Experimental designs that gauge SUTVA violations provide useful insights into the extent and influence of interpersonal communication. This article illustrates the value of one such design, a multilevel experiment in which treatments are randomly assigned to individuals and varying proportions of their neighbors. After describing the theoretical and statistical underpinnings of this design, we apply it to a large‐scale voter‐mobilization experiment conducted in Chicago during a special election in 2009 using social‐pressure mailings that highlight individual electoral participation. We find some evidence of within‐household spillovers but no evidence of spillovers across households. We conclude by discussing how multilevel designs might be employed in other substantive domains, such as the study of deterrence and policy diffusion.     

Evaluation of pediatric skull fracture imaging techniques

Radiologic imaging is crucial in the diagnosis of skull fracture, but there is some doubt as to whether different imaging modalities can accurately identify fractures present on a human skull. While studies have been performed to evaluate the efficacy of radiologic imaging at other anatomical locations, there have been no systematic studies comparing various CT techniques, including high resolution imaging with and without 3D reconstructions to conventional radiologic imaging in children, we investigated which imaging modalities: high-resolution CT scan with 3D projections, clinical-resolution CT scans or X-rays, best showed fracture occurrence in a pediatric human cadaver skull by having an expert pediatric radiologist examine radiologic images from fractured skulls. The skulls used were taken from pediatric cadavers ranging in age from 5 months to 16 years. We evaluated the sensitivity and specificity for the imaging modalities using dissection findings as the gold standard. We found that high-resolution CT scans with 3D projections and conventional CT provided the most accurate fracture diagnosis (single-fracture sensitivity of 71%) followed by X-rays (single-fracture sensitivity of 63%). Linear fractures outsider the region of the sutures were more identifiable than diastatic fractures, though the incidence of false positives was greater for linear fractures. In the two cases where multiple fractures were present on the same anatomical skull location, the radiologist was less likely to identify the presence of additional fractures than a single fracture. Overall, the high-resolution and clinical-resolution CT scans had the similar accuracy for detecting skull fractures while the use of the X-ray was both less accurate and had a lower specificity.     

Social Network Analysis and the Diffusion of the Strict Liability Rule for Manufacturing Defects, 1963–87

This article reports the results of a study that uses social network analysis to compare the persuasiveness of legal precedents in the diffusion of the strict liability rule for manufacturing defects. This new study tests which legal precedents were most influential and also whether certain state judicial variables influenced the diffusion process. The results are striking. The federal circuit regions appear to define an important reference group in the diffusion process, and social network effects dominate economic and political variables. In addition, the de facto separation of powers in the enactment of new state legislation appears to influence courts' propensities to adopt the strict liability rule. When the executive and legislative branches were controlled by the same political party, regardless of whether it was Republican or Democratic, state courts were more inclined to adopt the strict liability rule.     

A conversation with Donald Berwick on implementing national health reform

Michael Birnbaum interviews Donald Berwick shortly after his departure from the Centers for Medicare and Medicaid Services about the national health care landscape. Berwick discusses the strategic vision, policy levers, operational challenges, and political significance of federal health care reform. He rejects the notion that the Affordable Care Act represents a government takeover of health care financing or service delivery but says the law's Medicaid expansion and its creation of health benefit exchanges present a "watershed moment for American federalism." Berwick argues that the solution to Medicare's cost-containment challenge lies in quality improvement. He is optimistic that accountable care organizations can deliver savings and suggests that shifting risk downstream to providers throws the health insurance model into question. Finally, looking to the future, Berwick sees a race against time to make American health care more affordable.     

STR melting curve analysis as a genetic screening tool for crime scene samples

In this proof-of-concept study, high-resolution melt curve (HRMC) analysis was investigated as a postquantification screening tool to discriminate human CSF1PO and THO1 genotypes amplified with mini-STR primers in the presence of SYBR Green or LCGreen Plus dyes. A total of 12 CSF1PO and 11 HUMTHO1 genotypes were analyzed on the LightScanner HR96 and LS-32 systems and were correctly differentiated based upon their respective melt profiles. Short STR amplicon melt curves were affected by repeat number, and single-source and mixed DNA samples were additionally differentiated by the formation of heteroduplexes. Melting curves were shown to be unique and reproducible from DNA quantities ranging from 20 to 0.4 ng and distinguished identical from nonidentical genotypes from DNA derived from different biological fluids and compromised samples. Thus, a method is described which can assess both the quantity and the possible probative value of samples without full genotyping.     

City management,public administration and the American enlightenment

As the cost and size of government continues to escalate, there is a growing concern over increasing the efficiency and effectiveness in the delivery of public services. Productivity bargaining as one tool has Cained the attention of a small but growing number of public officials who see this technique as one rational method of resolving the conflicting pressures generated by the demand for government services on the one hand and limited resources on the other. The experience of one large metropolitan area with productivity bargaining is reviewed at some length.     

A Crisis of Authority? A Conversation with Alasdair Roberts about the Bush Years

Alasdair Roberts's recent book The Collapse of Fortress Bush: The Crisis of Authority in American Government is an appraisal of the George W. Bush administration's response to the 9/11 attacks and its management of the global war on terrorism. This war, Roberts argues, is a neoliberal war designed to accommodate assumptions about the boundaries of governmental action that became prevalent after Ronald Reagan's election to the presidency in 1980. Concerns about the renaissance of the "imperial presidency" are simplistic and misplaced, Roberts proposes, because they largely ignore how executive authority in the United States has been weakened by political, economic, and institutional forces. President Bush's actions after 9/11 reflect the limitations of his power. His White House was unable to impose significant burdens on citizens or the economy, felt forced to expand power surreptitiously, and chose to act militarily because the armed services enjoyed a level of legitimacy that was absent from the rest of government.