众数之误

文章指出:现行统计学教科书均把众数与中位数称之为位置平均数,但从其含义来看,众数不应是位置平均数;众数的计算确定方法也有值得商榷之处     

Ethical issues in tracking cellular telephones at an event

Early in 2007, the CSIR conducted an experiment to track the cellular telephones of a small group of people as they moved to and from an event, to test the viability of using such tracking to provide the participants with useful traffic information. This project raised a number of ethical issues, which prompted this paper and which we discuss here. These include:

• the ethics of modelling data, including the treatment of research participants;

• privacy and surveillance issues related to tracking the movement of people;

• the risks inherent in being tracked vs the benefits of being tracked; and

• the ethics related to sending messages to drivers.

We have reviewed the literature on ethics and used the results to assemble a check list of relevant ethical issues, adding a few of our own (i.e. a deontological ethics approach), against which the conduct of this research project was assessed. We also provide an overview of the experiment and the results obtained.     

On evaluating the performance of different forecasters

In this article, we have evaluated the performance of different forecasters and tested association between their performances for different pairs of variables. We have used three data sets of track records of professional U.S. economic forecasters participating in the Blue Chip consensus forecasting service (the data sets contain the root mean square errors (RMSE) of different forecasters for different years). To evaluate the performance of forecasters we have covered three well-known tests, namely the usual F test (cf. Fisher (1923 Fisher, R. A., Mackenzie, M. A. (1923). Studied in crop variation II. The manurial response of different potato. Journal of Agricultural Science 13:311–320. [Google Scholar])), Kruskal Wallis test (cf. Kruskal and Wallis (1952 Kruskall, W. H., Wallis, W. A. (1952). Use of ranks in one-criterion variance analysis. Journal of American Statistical Association 47:583–621. [Google Scholar])), and Extension of Median test (cf. Daniel (1990 Daniel, W. W. (1990). Applied Nonparametric Statistics. Duxbury Classic Series. (2nd Ed.), Boston. [Google Scholar])). To test the association between the forecaster's performances for different pairs of variables, we have considered Gini mean correlation coefficient r_g1 (cf. Yitzhaki, S., and Olkin, I. (1991 Yitzhaki, S., Olkin, I. (1991). Concentration indices and concentration curves, in K. Mosler and M. Scarsini (eds.), Stochastic Orders and Decisions under Risk, Institute of Mathematical Statistics: Lecture-Notes Monograph Series, 19, 1991, 380–392. [Google Scholar]) and Yitzhaki (2003 Yitzaki, S. (2003). Gini mean difference: A superior measure of variability for non normal distribution. Metron-International Journal of Statistics, LXI:285–316. [Google Scholar])), Modified rank correlation coefficient (cf. Zimmerman (1994 Zimmerman, D. W. (1994). A Note on modified rank correlation. Journal of educational and Behavioral Statistics 19:357–362. [Google Scholar])) and three modifications of Spearman rank correlation coefficient. We have observed that different forecasters do not necessarily offer same average performance. Moreover, an evidence of association between two criteria does not always lead us reaching at the same decision. The outcomes of the study may help the practitioners in selecting the best forecaster(s) for policymaking purposes.     

Fisher information in exponential-weighted location-scale distributions

In this article, the comparison between the Fisher information on parameters of the weighted distributions and the parent distributions is done. The most common family of distributions, location–scale family, is considered with the exponential weight function w(x) = e^βx where β is a constant. Conditions under which the weighted distributions are more (less) informative than the parent distribution are given. This was done for location, scale, and location–scale families when the scale parameter is considered as a nuisance parameter. Furthermore, using the transformation technique, we show that the results in location–scale family can be generalized to the broader classes of problems that studied the Fisher information of the weighted distributions such as Tzavelas and Economou (2014 Tzavelas, G., and P. Economou. 2014. Characterization properties based on the fisher information for weighted distributions. Statistics and Probability Letters 84:54–9.[Crossref], [Web of Science ®] , [Google Scholar]). As the exponential weight function can include some other weight functions, the obtained results in this article can be generalized for some other weight functions.     

Modeling the problem of locating collection areas for urban waste management. An application to the metropolitan area of Barcelona

Reverse logistics problems arising in municipal waste management are both wide-ranging and varied. The usual collection system in UE countries is composed of two phases. First, citizens leave their refuse at special collection areas where different types of waste (glass, paper, plastic, organic material) are stored in special refuse bins. Subsequently, each type of waste is collected separately and moved to its final destination (a recycling plant or refuse dump). The present study focuses on the problem of locating these collection areas. We establish the relationship between the problem, the set covering problem and the MAX-SAT problem and then go on to develop a genetic algorithm and a GRASP heuristic to, respectively, solve each formulation. Finally, the quality of the algorithms is tested in a computational experience with real instances from the metropolitan area of Barcelona, as well as a reduced set of set covering instances from the literature.     

Homogeneity test based on ranked set samples

Abstract

The homogeneity hypothesis is investigated in a location family of distributions. A moment-based test is introduced based on data collected from a ranked set sampling scheme. The asymptotic distribution of the proposed test statistic is determined and the performance of the test is studied via simulation. Furthermore, for small sample sizes, the bootstrap procedure is used to distinguish the homogeneity of data. An illustrative example is also presented to explain the proposed procedures in this paper.     

以螺纹为基准的夹具定位误差分析

对开口螺套和螺纹定位块这两种定位元件进行了定位误差分析。     

The Place of Place: Location and Immigrant Economic Well-being in Canada

In recent years, successive cohorts of immigrants to Canada have experienced a striking level of deterioration in their economic well-being. At the same time, more immigrants than ever before are choosing to live in Montréal, Toronto, or Vancouver, Canada’s three-first-tier or ‘gateway cities’. This paper uses instrumental variable regression techniques to determine the extent to which gateway city clustering is related to immigrant economic well-being. It identifies whether employment status, earnings, and employment suitability would significantly improve if more immigrants chose to live outside of Canada’s three gateway cities. The results suggest that, for the most part, although immigrants do worse than the native-born in gateway cities, they do experience marginally higher earnings than their non-gateway counterparts. Income and unemployment rates are higher for immigrants in gateway cities than they are for the native-born, but the gateway/non-gateway disparity is minimal. Levels of employment mismatch are substantially higher in gateway cities, compared to both the gateway city native-born population, and non-gateway immigrants. An analysis of the data shows that only marginal improvements to economic well-being would result from an increase in non-gateway immigration, and that there are other factors, like race or skin colour, that seem to be more closely linked to labour market success.

APPLICATION OF AN EXPECTED COVERING MODEL TO EMERGENCY MEDICAL SERVICE SYSTEM DESIGN*

The Emergency Medical Service (EMS) Act specifies the fraction of all demands for service that must be reached in a given amount of time for urban and rural areas. The conditions have traditionally been interpreted to apply to the case in which all EMS vehicles are available to respond to demands. A model that considers the probability of a vehicle being busy is formulated and model properties are briefly discussed. The model is then applied to two problems: a 55-node test case and a 33-node census tract representation of Austin, Texas. The implications of the new model for EMS system design are discussed as are the limitations of the modeling approach.     

A FACILITY LOCATION PROBLEM WITH DISTANCE-DEPENDENT DEMAND

This paper examines network systems where demand for the services of a facility originates at the nodes of the network and its magnitude depends on the shortest distance to a service-providing facility. Service systems with such features include bank branches, fastfood outlets, and grocery stores. With the assumption that demand is a Poisson-distributed random variable whose mean is an exponentially decreasing function of distance, possible locations based on two important performance measures are characterized: the expected value and the variance of the demand. Two procedures are proposed: one to find the locations with the minimum and maximum expected demand and the other to find the location(s) that provide a given level of expected demand. The procedures are illustrated by two examples.