To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We have previously shown that the minor alleles of vascular endothelial growth factor A (VEGFA) single-nucleotide polymorphism rs833069 and superoxide dismutase 2 (SOD2) single-nucleotide polymorphism rs2758331 are both associated with improved transplant-free survival after surgery for CHD in infants, but the underlying mechanisms are unknown. We hypothesised that one or both of these minor alleles are associated with better systemic ventricular function, resulting in improved survival.
This study is a follow-up analysis of 422 non-syndromic CHD patients who underwent neonatal cardiac surgery with cardiopulmonary bypass. Echocardiographic reports were reviewed. Systemic ventricular function was subjectively categorised as normal, or as mildly, moderately, or severely depressed. The change in function was calculated as the change from the preoperative study to the last available study. Stepwise linear regression, adjusting for covariates, was performed for the outcome of change in ventricular function. Model comparison was performed using Akaike’s information criterion. Only variables that improved the model prediction of change in systemic ventricular function were retained in the final model.
Genetic and echocardiographic data were available for 335/422 subjects (79%). Of them, 33 (9.9%) developed worse systemic ventricular function during a mean follow-up period of 13.5 years. After covariate adjustment, the presence of the VEGFA minor allele was associated with preserved ventricular function (p=0.011).
These data support the hypothesis that the mechanism by which the VEGFA single-nucleotide polymorphism rs833069 minor allele improves survival may be the preservation of ventricular function. Further studies are needed to validate this genotype–phenotype association and to determine whether this mechanism is related to increased vascular endothelial growth factor production.
In order to encouragee broad participation in deliberative forums, it is important to understand how people from politically less powerful groups perceive the deliberative experience and how discussion group composition affects their experiences. Using data from 27 deliberative polls from 2004, we examine how four individual characteristics (sex, age, race, and education) and randomly assigned small group composition predict participants’ attitudes about the deliberative experience. We find evidence that women, young people, non-whites, and those without college degree generally evaluate the experience positively, but find no evidence for the argument that including more people from these groups would lead to more positive deliberation experience for participants from the groups. That is, there is no interaction between minority status and group composition in predicting participants’ evaluation of the deliberation process.
Political scientists often analyze data in which the observational units are clustered into politically or socially meaningful groups with an interest in estimating the effects that group-level factors have on individual-level behavior. Even in the presence of low levels of intracluster correlation, it is well known among statisticians that ignoring the clustered nature of such data overstates the precision estimates for group-level effects. Although a number of methods that account for clustering are available, their precision estimates are poorly understood, making it difficult for researchers to choose among approaches. In this paper, we explicate and compare commonly used methods (clustered robust standard errors (SEs), random effects, hierarchical linear model, and aggregated ordinary least squares) of estimating the SEs for group-level effects. We demonstrate analytically and with the help of empirical examples that under ideal conditions there is no meaningful difference in the SEs generated by these methods. We conclude with advice on the ways in which analysts can increase the efficiency of clustered designs.
Experiments conducted in the field allay concerns over external validity but are subject to the pitfalls of fieldwork. This article proves that scalable protocols conserve statistical efficiency in the face of problems implementing the treatment regime. Three designs are considered: randomly ordering the application of the treatment; matching subjects into groups prior to assignment; and placebo-controlled experiments. Three examples taken from voter mobilization field experiments demonstrate the utility of the design principles discussed.
College students are young, have little or no history of voting, and are residentially mobile, which makes them a population in great need of registering to vote. Universities have a civic, pedagogical, and legal obligation to register their students to vote. In 2006, we conducted a controlled experiment across 16 college campuses to test the efficacy of classroom presentations to increase voter registration. The 25,256 students across more than 1,026 classrooms were randomly assigned to one of three conditions: (1) a control group receiving no presentation; (2) a presentation by a professor; and (3) a presentation by a student volunteer. Verifying registration and voter turnout from a national voter database, we found that both types of presentations increased overall registration by 6 percentage points and turnout rates by approximately 2.6 percentage points. These results demonstrated that universities can take simple steps to engage their students in politics.
The provision of surgery within humanitarian crises is complex, requiring coordination and cooperation among all stakeholders. During the 2011 Humanitarian Action Summit best practice guidelines were proposed to provide greater accountability and standardization in surgical humanitarian relief efforts. Surgical humanitarian relief planning should occur early and include team selection and preparation, appropriate disaster-specific anticipatory planning, needs assessment, and an awareness of local resources and limitations of cross-cultural project management. Accurate medical record keeping and timely follow-up is important for a transient surgical population. Integration with local health systems is essential and will help facilitate longer term surgical health system strengthening.
Civic participation is an essential component of a healthy democracy. Voting allows citizens to communicate preferences to elected officials and influence who holds public office. At the same time, deficiencies and asymmetries of participation in the United States call into question the representativeness of elected officials and public policies. Yet, although political activity is crucial for the equal protection of interests, participation is often seen by individuals as irrational or excessively costly, and it is well known that turnout in the United States lags well behind that of other democracies. Scholars have consistently found that participation is linked to socioeconomic variables, psychological orientations, and recruitment. Candidates, parties, and organizations thus spend considerable effort mobilizing electoral activity. This chapter highlights contributions made by field experiments to the study of voter mobilization, the problems faced by such work, and opportunities for future study.
Nonexperimental studies have primarily relied on survey research to demonstrate correlations between self-reported mobilization and civic-minded behaviors, while also controlling for demographic characteristics (e.g., age, education, income) that are known to be significant predictors of turnout. The conclusion usually reached is that mobilization efforts are generally effective (e.g., Rosenstone and Hansen 1993; Verba, Schlozman, and Brady 1995). However, four major empirical hurdles render this conclusion suspect.
People are embedded in networks, neighborhoods, and relationships. Understanding the nature of our entanglements and how they shape who we are is fundamental to social sciences. Networks are likely to explain important parts of personal development and contemporary decision making. Researchers have found social networks to be important in activities as disparate as voting (Berelson, Lazarsfeld, and McPhee 1954), immigration patterns (Sanders, Nee, and Sernau 2002), finding a job (Nordenmark 1999), recycling (Tucker 1999), deworming (Miguel and Kremer 2004), cardiovascular disease and mortality (Kawachi et al. 1996), writing legislation (Caldeira and Patterson 1987), and even happiness (Fowler and Christakis 2008). A wide range of political outcomes could be studied using social networks; the only limitation is that the outcome be measurable. Ironically, the very ubiquity and importance of social networks make them difficult to study. Isolating causal effects is always difficult, but when like-minded individuals cluster together, share material incentives, are exposed to common external stimuli, and simultaneously influence each other, the job of reliably estimating the importance of social ties becomes nearly impossible. Rather than offering a comprehensive overview of the wide number of topics covered by social networks, this chapter focuses on the common empirical challenges faced by studies of social networks by considering the challenges faced by observational studies of social networks, discussing laboratory approaches to networks, and describing how network experiments are conducted in the field. The chapter concludes by summarizing the strengths and weaknesses of the different approaches and considers directions for future work.
Members of the same household share similar voting behaviors on average, but how much of this correlation can be attributed to the behavior of the other person in the household? Disentangling and isolating the unique effects of peer behavior, selection processes, and congruent interests is a challenge for all studies of interpersonal influence. This study proposes and utilizes a carefully designed placebo-controlled experimental protocol to overcome this identification problem. During a face-to-face canvassing experiment targeting households with two registered voters, residents who answered the door were exposed to either a Get Out the Vote message (treatment) or a recycling pitch (placebo). The turnout of the person in the household not answering the door allows for contagion to be measured. Both experiments find that 60% of the propensity to vote is passed onto the other member of the household. This finding suggests a mechanism by which civic participation norms are adopted and couples grow more similar over time.
Email your librarian or administrator to recommend adding this to your organisation's collection.