Wait-and-See or Step in? Dynamics of Interventions

We study the optimal intervention policy to stop projects in a relational contract between a principal and a policymaker. The policymaker is privately informed about his ability and privately chooses how much effort to exert. Before a project is completed, the principal receives a signal about its outcome and can intervene to stop it. Intervention may prevent a bad outcome, but no intervention leads to better learning about the policymaker’s ability. In the benchmarks with observable effort or observable ability, optimal intervention follows a threshold rule. With unobservable effort and ability, the optimal policy switches between intervention and no intervention. (JEL D78, D82, D86)

Problems with diagnosing early stadia of scoliosis due to discrepancies between ATR and the Cobb angle

Background This research analysed discrepancies between the angle of trunk rotation (ATR) and the Cobb angle, in order to study if the commonly used 7° cut-off threshold for ATR helps diagnose scoliosis. In early stadia of scoliosis in children, ATR and the Cobb angle often disagree, increasing the risk of a false diagnosis: while the former does not suggest scoliosis, the latter does. Methods The study analysed ATR clinical parameters and the Cobb angle in the X-ray pictures of 117 (23 boys and 94 girls, aged 6–17 years) children who had not yet started treatment and whose X-ray pictures showed the Cobb angle of at least 10°, indicating idiopathic scoliosis. The degrees of lumbar lordosis and thoracic kyphosis were measured using the Saunders inclinometer, and back asymmetry was measured with Adam’s forward bend test using the Bunnell scoliometer. In the X-ray pictures, the curvature angle was plotted according to the Cobb method. The patients were stratified based on their age, and their ATRs and Cobb angles were compared. Results Although all the children had the Cobb angle over 10°, in 69 out of 117 (59%), ATR was below 7%. So, using the 7° cut-off threshold rule, scoliosis would not be diagnosed in those children. This shows that the two tests often disagree, suggesting that the 7° cut-off threshold or ATR is ineffective in diagnosing scoliosis. Conclusions To improve the method for diagnosing scoliosis based on ATR, consideration should be given to lowering the 7° ATR cut-off threshold.

Strengthening the Multi-Party Presidential Government in Indonesia

The Multi-Party Presidential Government in Indonesia has reached a critical point. The 2.5 percent parliamentary threshold rule in the 2009 Election was incapable to address the issue. The parliamentary threshold was raised to 3.5 percent in 2014, in the hope to reduce the number of party joining the election, but it failed to do so. There were 9 national parties participating in the 2009 election, and it will be increased to 16 in the 2019 election. Theoretically, the combination of multi-party parliament in a Presidential Government is rather strange. It is not surprising that the "conflict" between the president and parliament often occurs. There suppose to be a coalition supporting the government in parliament, but the coalition is not a firm one. The coalition did not have a significant influence in strengthening the presidential government. Therefore, this study intends to provide a complete picture of multi-party system practices while trying to provide solutions for strengthening the presidential government in Indonesia. To achieve this goal, this study uses the literature study method in collecting relevant information, using a qualitative approach. This approach is considered appropriate because multi-party phenomena and presidential systems are multidimensional. In contrast to previous research which was limited to the description and problems of multiparty systems, this research besides describing the system of government also provided moderate solutions that were considered to be in accordance with the Indonesian context. This study assumes that strengthening presidential systems can be done if the political parties are more modest. In addition, parliamentary support for the president must be optimized. The results of the study concluded that the strengthening of presidential systems must be carried out through the purification of the government system contained in the constitution, forming and strengthening the ranks of government coalitions in parliament, and carrying out a number of institutional engineering through various forms. These three things must be wrapped in a constitutional frame (amendments to the 1945 Constitution) and regulations (revisions to laws and government regulations). The amendments and revisions can be done through three corridors, namely the intra-parliamentary movement, the extra-parliamentary movement, and the referendum.

Outlier detection for multinomial data with a large number of categories

This paper develops an outlier detection procedure for multinomial data when the number of categories tends to infinity. Most of the outlier detection methods are based on the assumption that the observations follow multivariate normal distribution, while in many modern applications, the observations either are measured on a discrete scale or naturally have some categorical structures. For such multinomial observations, there are rather limited approaches for outlier detection. To overcome the main obstacle, the least trimmed distances estimator for multinomial data and a fast algorithm to identify the clean subset are introduced in this work. Also, a threshold rule is considered through the asymptotic distribution of measure distance to identify outliers. Furthermore, a one-step reweighting scheme is proposed to improve the efficiency of the procedure. Finally, the finite sample performance of our method is evaluated through simulations and is compared with that of available outlier detection methods.

Explore/exploit tradeoff strategies in a resource accumulation search task

How, and how well, do people switch between exploration and exploitation to search for and accumulate resources? We study the decision processes underlying such exploration/exploitation tradeoffs by using a novel card selection task. With experience, participants learn to switch appropriately between exploration and exploitation and approach optimal performance. We model participants’ behavior on this task with random, threshold, and sampling strategies, and find that a linear decreasing threshold rule best fits participants’ results. Further evidence that participants use decreasing threshold-based strategies comes from reaction time differences between exploration and exploitation; however, participants themselves report non-decreasing thresholds. Decreasing threshold strategies that “front-load” exploration and switch quickly to exploitation are particularly effective in resource accumulation tasks, in contrast to optimal stopping problems like the Secretary Problem requiring longer exploration.

Prospects on Hungarian as a Regional Official Language and Szeklerland’s Territorial Autonomy in Romania

This article analyses two options the Hungarian ethno-linguistic community in the Transylvanian region of Romania has in order to preserve its ethno-linguistic identity. Firstly, there is the option of unrestricted language use in the public domain. At present the Romanian legal framework assigns members of the Hungarian speaking community in Transylvania individual linguistic and cultural rights only. The Romanian language policy is further restricted by a threshold rule. The ratio of minority must number 20 per cent of the total inhabitants of a certain administrative-territorial unit in order to have their language recognised officially. The second possibility is that historical territories where Transylvanian Hungarians statistically form a dominant majority (i.e. Szeklerland) are granted territorial autonomy. The territoriality principle would secure linguistic minority rights. We will conclude that the prospects for Hungarian as a regional language in Romania are more realistic than the recognition of Szeklerland’s territorial autonomy.

Risk Algorithm Using Serial Biomarker Measurements Doubles the Number of Screen-Detected Cancers Compared With a Single-Threshold Rule in the United Kingdom Collaborative Trial of Ovarian Cancer Screening

Purpose Cancer screening strategies have commonly adopted single-biomarker thresholds to identify abnormality. We investigated the impact of serial biomarker change interpreted through a risk algorithm on cancer detection rates. Patients and Methods In the United Kingdom Collaborative Trial of Ovarian Cancer Screening, 46,237 women, age 50 years or older underwent incidence screening by using the multimodal strategy (MMS) in which annual serum cancer antigen 125 (CA-125) was interpreted with the risk of ovarian cancer algorithm (ROCA). Women were triaged by the ROCA: normal risk, returned to annual screening; intermediate risk, repeat CA-125; and elevated risk, repeat CA-125 and transvaginal ultrasound. Women with persistently increased risk were clinically evaluated. All participants were followed through national cancer and/or death registries. Performance characteristics of a single-threshold rule and the ROCA were compared by using receiver operating characteristic curves. Results After 296,911 women-years of annual incidence screening, 640 women underwent surgery. Of those, 133 had primary invasive epithelial ovarian or tubal cancers (iEOCs). In all, 22 interval iEOCs occurred within 1 year of screening, of which one was detected by ROCA but was managed conservatively after clinical assessment. The sensitivity and specificity of MMS for detection of iEOCs were 85.8% (95% CI, 79.3% to 90.9%) and 99.8% (95% CI, 99.8% to 99.8%), respectively, with 4.8 surgeries per iEOC. ROCA alone detected 87.1% (135 of 155) of the iEOCs. Using fixed CA-125 cutoffs at the last annual screen of more than 35, more than 30, and more than 22 U/mL would have identified 41.3% (64 of 155), 48.4% (75 of 155), and 66.5% (103 of 155), respectively. The area under the curve for ROCA (0.915) was significantly (P = .0027) higher than that for a single-threshold rule (0.869). Conclusion Screening by using ROCA doubled the number of screen-detected iEOCs compared with a fixed cutoff. In the context of cancer screening, reliance on predefined single-threshold rules may result in biomarkers of value being discarded.

BOOTSTRAP PERCOLATION ON RANDOM GEOMETRIC GRAPHS

Bootstrap percolation (BP) has been used effectively to model phenomena as diverse as emergence of magnetism in materials, spread of infection, diffusion of software viruses in computer networks, adoption of new technologies, and emergence of collective action and cultural fads in human societies. It is defined on an (arbitrary) network of interacting agents whose state is determined by the state of their neighbors according to a threshold rule. In a typical setting, BP starts by random and independent “activation” of nodes with a fixed probabilityp, followed by a deterministic process for additional activations based on the density of active nodes in each neighborhood (θ activated nodes). Here, we study BP on random geometric graphs (RGGs) in the regime when the latter are (almost surely) connected. Random geometric graphs provide an appropriate model in settings where the neighborhood structure of each node is determined by geographical distance, as in wirelessad hocand sensor networks as well as in contagion. We derive boundspc′,pc″ on the critical thresholds such that for allp > p″cfull percolation takes place, whereas forp < p′cit does not. We conclude with simulations that compare numerical thresholds with those obtained analytically.

Performance Analysis of Radar and ESM Track Association Algorithms

Statistical theory and fuzzy analysis are two primary methods of radar and ESM track association algorithms. Absolute-double-threshold rule was used to analyze these two association algorithms. Each algorithm was simulated in this paper. The simulation results show that both of these two track association algorithms have high probability of correct association, but the algorithm based on statistical theory has faster convergent speed and litter samples, while the other is simple, and has less calculation.