Distribution-free tests for comparing several treatments with a control

Abstract  In this paper we propose distribution-free treatments versus control tests for the one- and two-way classifications. The null distribution properties are shown to be equivalent to those of well-known statistics for which critical values have been extensively tabled. Asymptotic relative efficiencies with respect to corresponding normal theory competitors are derived and optimal designs for the allocation of experimental units to the treatments and control are obtained.     

A logistic regression point of view toward loss given default distribution estimation

We propose a new procedure to estimate the loss given default (LGD) distribution. Owing to the complicated shape of the LGD distribution, using a smooth density function as a driver to estimate it may result in a decline in model fit. To overcome this problem, we first apply the logistic regression to estimate the LGD cumulative distribution function. Then, we convert the result into the LGD distribution estimate. To implement the newly proposed estimation procedure, we collect a sample of 5269 defaulted debts from Moody’s Default and Recovery Database. A performance study is performed using 2000 pairs of in-sample and out-of-sample data-sets with different sizes that are randomly selected from the entire sample. Our results show that the newly proposed procedure has better and more robust performance than its alternatives, in the sense of yielding more accurate in-sample and out-of-sample LGD distribution estimates. Thus, it is useful for studying the LGD distribution.     

GIS as a tool for selection of sample areas in a travel behaviour survey

Whilst Geographical Information Systems (GIS) are now used more commonly in transport research and modelling, GIS techniques were used in this study to select similar sample areas (in terms of geography and census attributes) for data collection. For this purpose, a GIS mapping system for Tyne and Wear, UK, was built. The system included topographic maps of the area, boundary maps of Lower Super Output Areas (LSOA), and aggregated census statistics datasets for LSOAs. Criteria relating to census attributes and the nature of transport were employed to identify ‘hotspots’ by GIS enquiry to provide suitably matching areas, which then formed the basis of the sampling frame.The research project was concerned with commuters’ travel choices and so the study needed to identify commuters. In this case-study context, it is not possible to select fully homogeneous areas, so the GIS ‘hotspots’ approach allowed the identification of areas where there were a high concentration of commuters with multiple alternatives for travel to work. A pilot study showed that the GIS origin-based approach was good in collecting a balanced sample, as compared to an employment-based destination survey. This paper explores the benefits and costs of these origin- and destination-based approaches. In the origin-based home sample, households with paper-based surveys were targeted after identification by GIS. This origin approach requires more data preparation compared to the alternative of an employer-based, destination-based sample that could use online survey methodologies.The paper concludes by identifying GIS as an important tool in selecting a sample area for data collection using multiple criteria, but argues that plans for data collection need to be flexibly constructed to overcome unexpected challenges. Although this paper focuses on a transport research case study, the methodology presented can be applied to survey design and selection of sample areas in other disciplines.     

Foreign Direct Investment in the Enlarged EU: Do Taxes Matter and to What Extent?

Foreign direct investment is of increasing importance in the European Union. This paper estimates the effect of taxes on foreign direct investment (FDI) flows and on three sub-components of these flows for the countries of the enlarged European Union. The model in the spirit of gravity equations robustly explains FDI flows between the 25 member states. Sample selection needs to be addressed in the estimation. We show that the different subcomponents of FDI should and indeed do react differently to taxes. After controlling for unobserved country characteristics and common time effects, the top statutory corporate tax rate of both, source and host country, turn insignificant for total FDI and investment into equity. However, high source country taxes clearly increase the probability of firms to re-invest profits abroad and lower the percentage of debt financed FDI. This might reflect profit re-allocation to avoid taxes. Market size factors have the expected signs.

电感耦合等离子体发射光谱法测定蜂蜜中7种矿物元素的含量

为了快速直接测定蜂蜜中多种矿物元素的含量,采用电感耦合等离子体发射光谱(ICP-AES)法建立了同时测定蜂蜜中钙、钾、镁、钠、锌、铁、铜7种矿物元素含量的方法,考察了方法的标准曲线线性关系、检出限、精密度和准确度,讨论了前处理方法、不同产地以及蜜源植物种类对各元素含量的影响。结果表明:线性相关系数达到0.999 9以上,方法检出限为0.003～0.030 mg/L,相对标准偏差低于2%,回收率为88.66%～105.31%;不同产地的洋槐蜜中,河北洋槐蜜的钙、钾含量明显高于其他地区,广西洋槐蜜的钠、铁含量最高;不同蜜源植物的蜂蜜中,河北枣花蜜的铁含量最高,野生蜜中各种矿物元素都较为丰富。电感耦合等离子体发射光谱法可以快速、同时测定蜂蜜中多种矿物元素含量,方法简便易行,结果准确可靠,可为蜂蜜品质鉴定以及人们对蜂蜜的合理选择提供参考。     

Pricing a rural development program: uncertainty,indifference, and protest behaviors

This article presents an econometric approach to modeling uncertainty, unwillingness to pay, and protest behavior in contingent valuation studies. For that purpose, a mixture model with sample selection is developed for a multiple‐bounded uncertainty elicitation format. The proposed theoretical framework is applied to evaluate the social welfare impact of implementing a sustainable rural development program. Results show that a “naive” analytical approach that excludes protesters from the analysis would result in significantly higher willingness to pay estimates for those individuals who favor the implementation of the program and agree to reveal their true reservation prices.     

HEDONIC PRICE INDEXES FOR RESIDENTIAL HOUSING: A SURVEY,EVALUATION AND TAXONOMY

Every house is different. It is important that house price indexes take account of these quality differences. Hedonic methods which express house prices as a function of a vector of characteristics (such as number of bedrooms and bathrooms, land area and location) are particularly useful for this purpose. I consider here some developments in the hedonic methodology, as it is applied in a housing context, that have occurred in the last three decades. A number of hedonic house price indexes are now available. However, it is often difficult to see how these indexes relate to each other. For this reason I attempt to impose some structure on the literature by developing a taxonomy of hedonic indexes, and then show how existing indexes fit into this taxonomy. Also discussed are some promising areas for future research in the hedonic field. In particular, greater use needs to be made of spatial econometric and nonparametric methods to exploit the increased availability of geospatial data. The main criticisms of the hedonic approach are evaluated and compared with those of the repeat‐sales and stratified median methods. The overall conclusion is that the advantages of the hedonic approach outweigh its disadvantages.     

Estimating panel data models in the presence of endogeneity and selection

We consider estimation of panel data models with sample selection when the equation of interest contains endogenous explanatory variables as well as unobserved heterogeneity. Assuming that appropriate instruments are available, we propose several tests for selection bias and two estimation procedures that correct for selection in the presence of endogenous regressors. The tests are based on the fixed effects two-stage least squares estimator, thereby permitting arbitrary correlation between unobserved heterogeneity and explanatory variables. The first correction procedure is parametric and is valid under the assumption that the errors in the selection equation are normally distributed. The second procedure estimates the model parameters semiparametrically using series estimators. In the proposed testing and correction procedures, the error terms may be heterogeneously distributed and serially dependent in both selection and primary equations. Because these methods allow for a rather flexible structure of the error variance and do not impose any nonstandard assumptions on the conditional distributions of explanatory variables, they provide a useful alternative to the existing approaches presented in the literature.     

原水预处理设备改造

水的预处理主要任务是除去水中的悬浮物和胶体,为除去溶解物质打好基础。预处理的方法主要有混凝处理、澄清处理和过滤处理。某电厂使用的澄清设备是机械加速澄清池,本文就该电厂原水预处理设备在调试过程中机械搅拌澄清池出现的问题进行了分析,并提出了解决方法,对设备进行了改造。     

The impact of auctions on residential property prices

This study assesses whether the sale method in residential real estate markets – auction versus private treaty – is a determinant of sale price. Utilising a larger and richer dataset than previous research, we test for a price effect in auction sales in Sydney and Christchurch. When self‐selection biases are corrected for, using two‐stage hedonic regression analysis and a matched sampling procedure, we find no significant difference between prices of properties sold at auction to those sold by private treaty. This conflicts with the conclusions of previous research in the Australian and New Zealand housing markets, which have documented a price premium associated with auction sales.