Measuring Bias and Uncertainty in Ideal Point Estimates via the Parametric Bootstrap

Keith T. Poole Center for Advanced Study in the Behavioral Sciences and Department of Political Science, University of Houston, Houston, TX 77204-3011 e-mail: kpoole{at}uh.edu Over the last 15 years a large amount of scholarship in legislativepolitics has used NOMINATE or other similar methods to constructmeasures of legislators' ideological locations. These measuresare then used in subsequent analyses. Recent work in politicalmethodology has focused on the pitfalls of using such estimatesas variables in subsequent analysis without explicitly accountingfor their uncertainty and possible bias ( Herron and Shotts2003, Political Analysis 11:44–64). This presents a problemfor those employing NOMINATE scores because estimates of theirunconditional sampling uncertainty or bias have until now beenunavailable. In this paper, we present a method of forming unconditionalstandard error estimates and bias estimates for NOMINATE scoresusing the parametric bootstrap. Standard errors are estimatedfor the 90th U.S. Senate in two dimensions. Standard errorsof first–dimension placements are in the 0.03 to 0.08range. The results are compared with those obtained using theMarkov chain Monte Carlo estimator of Clinton et al. (2002,Stanford University Working Paper). We also show how the bootstrapcan be used to construct standard errors and confidence intervalsfor auxiliary quantities of interest such as ranks and the locationof the median senator.     

Self-reported suicidal behavior in juvenile offenders in custody: prevalence and associated factors

Suicide rates in prisons in England and Wales are high, including those in juvenile detention centers. Previous deliberate self-harm (DSH) is the strongest predictor of suicide in the general population. There is limited information on how many juvenile offenders (15 to 18 year-olds) have a history of DSH at the time of entering custody, or on factors associated with previous DSH. We aimed to determine the prevalence of previous DSH and suicidal ideation in a population of juvenile offenders in custody and to identify factors associated with DSH and suicidal ideation. Seven out of 45 subjects (15.6%) reported an act of DSH in the past. Twelve (26.6%) reported past suicidal ideation. Peer relationship difficulties and sexual abuse were significantly associated with DSH (p < 0.05). Other factors showed a trend toward being more common among those with DSH, but the premature ending of the project by the juvenile detention center prevented full investigation of the extent of DSH and associated factors. Nevertheless, the results indicated a much higher rate of DSH in this population than in young males in the community. A larger joint project with juvenile detention centers is required to confirm the extent of previous DSH at the time young offenders are admitted, and the associated risk factors, in order to assist prevention and intervention strategies.     

Economic and legal analysis of medical ethics

In the last decade, the antityrust authorities have stricken one after another of the ethical rules of professional societies. Underlying this pokicy is the widelyaccepted notion that ethics are simply devices designed by the professions to limit competition and thereby to benefit their pecuniary interests. The antitrust assault does not consider the longstanding, nearly universal consumer support for controls on the activities of certain professions. In this paper, the narrow view ofcompetition adopted by the courts is assailed. Focusing on the case ofrestrictions on interactions between physicians and other nonmedical health care providers, some procompetitive effects of medical ethics are analyzed. Generally, professional ethics can only change the form of competition but not eliminate it. A proper legal policy requires recognition of the consumer concern with the form of competition and therefore requires a careful balancing of the beneficial competitive effects against any attendant limits on intraprofessional competition.     

'Incidents' and foreign policy: A case study

Anglo-Russian relations during the period 1894-1914 were filled with incidents in large part stemming from the very different social and political frameworks of the two countries. The two countries had sharply differing traditions concerning individual liberty, freedom of the press and other such matters usually covered by the rubric of human rights. While the realities of great power politics forced the two countries to work together, it is not surprising that their collaboration was often marred by clashes of political and social sensibilities.