Chain ratio and regression type estimators for median estimation in survey sampling

In this paper, we consider chain ratio and regression type estimators for estimating median in survey sampling. We find expressions for the variance of the chain-ratio and chain-regression type estimators considered in the present investigation. The optimum values of the first phase and second phase sample sizes are also obtained for the fixed cost of survey. The relative efficiency of chain-ratio and chain-regression type estimators have been studied in comparison to ratio and regression type estimators of median proposed by Singh, Joarder and Tracy (2001).     

Almost unbiased ratio and product estimators based on interpenetrating subsamples

This paper proposes two classes of almost unbiased ratio and product estimators, in the case of interpenetrating subsample designs, which include the estimators considered by earlier authors. Several other almost unbiased ratio and product estimatbrs are given whlch are particular members of the proposed classes of estimators. Optimum estimators are also identified in these classes.     

A Class of Estimators of Population Variance Using Auxiliary Information in Sample Surveys

This article advocates the problem of estimating the population variance of the study variable using information on certain known parameters of an auxiliary variable. A class of estimators for population variance using information on an auxiliary variable has been defined. In addition to many estimators, usual unbiased estimator, Isaki's (1983), Upadhyaya and Singh's (1999), and Kadilar and Cingi's (2006) estimators are shown as members of the proposed class of estimators. Asymptotic expressions for bias and mean square error of the proposed class of estimators have been obtained. An empirical study has been carried out to judge the performance of the various estimators of population variance generated from the proposed class of estimators over usual unbiased estimator, Isaki's (1983), Upadhyaya and Singh's (1999) and Kadilar and Cingi's (2006) estimators.     

中国高速铁路是否显著影响城市土地利用——来自站点、线路和典型城市土地利用变化的回答

当前中国高速铁路正处于快速、全面发展阶段,研究高速铁路对城市土地利用的影响,对城市规划、城市与高速铁路的协调发展等均具有重要意义。利用GIS等技术提取已开通高速铁路站点周边、线路两侧土地利用数据以及部分城市高铁站点周边建设用地重心,从不同空间、城市类型、开通时间等角度对提取结果进行统计分析和图形对比。结果表明：高速铁路能通过促进各类型土地向建设用地转移来影响城市土地利用;高速铁路对站点周边土地利用的影响要大于对线路两侧的影响;高速铁路对城市土地利用的影响因城市规模类型不同而不同,对站点周围土地利用的影响总体有城市规模越大影响越大的特征,对特大城市、超大城市和县线路两侧土地利用的影响大于大中城市;高速铁路对城市土地利用的影响在时间上有递延性,在空间上有衰减性。     

Gavel-to-Gavel Congressional Television Coverage as Political Advertising: The Impact of C-Span on Legislative Sessions

This article examines the effect of television on the length of legislative sessions at the federal level in the United States. Data from the U.S. Congress during the period 1972–96 are employed, during part of which time each house of Congress received significant television coverage by C-SPAN and C-SPAN2. Evidence from a Parks regression suggests that the presence of C-SPAN has increased House sessions by 88–250 hours and the presence of C-SPAN2 has increased Senate sessions by a striking 252–431 hours, other things constant. Additional estimates suggest that House sessions are about two minutes longer per bill introduced under the eye of C-SPAN, and Senate sessions are about four minutes longer per bill introduced in the presence of C-SPAN2. Longer sessions, which represent low-cost forms of advertising for incumbents, are not without costs to taxpayers. We estimate that these costs lie somewhere between $16 million and $392 million in real terms per session of Congress.     

Foodgrain price stabilization: Implications of private storage and subsidized food distribution

Through simulation exercises, this paper explores the implications of private storage and subsidized distribution of foodgrain for price stabilization policies in India. A multi-market equilibrium approach is used to incorporate the simultaneity in the determination of supply and demand for the three major cereals, namely, rice, wheat, and coarse cereals. The policy implications of the results obtained are relevant to the current debate on agricultural policy reforms in India.     

On the Hardness of Approximating the Min-Hack Problem

We show several hardness results for the Minimum Hacking problem, which roughly can be described as the problem of finding the best way to compromise a target node given a few initial compromised nodes in a network. We give several reductions to show that Minimum Hacking is not approximable to within where δ = 1− ^c n, for any c < 1/2. We also analyze some heuristics on this problem.