Easy Implementation of Writing in Introductory Statistics Courses

In the past decade there has been a substantial increase in the number of introductory statistics courses taught at the undergraduate level. Many have argued successfully for the extensive use of writing in such courses in an attempt to highlight the interdisciplinary role of statistics and acknowledge that a good statistician must also be good at summarizing his or her analyses to nonstatisticians. This point was made by Radke-Sharpe, who went on to add that incorporating writing demands time, energy, and creativity, but that it is usually well worth the effort. This article discusses the efforts made by the authors to include writing in their courses, and some of the techniques that made the writing process painless and productive for both students and faculty.     

Stylometric analyses using Dirichlet process mixture models

Stylometry refers to the statistical analysis of literary style of authors based on the characteristics of expression in their writings. We propose an approach to stylometry based on a Bayesian Dirichlet process mixture model using multinomial word frequency data. The parameters of the multinomial distribution of word frequency data are the “word prints” of the author. Our approach is based on model-based clustering of the vectors of probability values of the multinomial distribution. The resultant clusters identify different writing styles that assist in author attribution for disputed works in a corpus. As a test case, the methodology is applied to the problem of authorship attribution involving the Federalist papers. Our results are consistent with previous stylometric analyses of these papers.     

发展尺度的演进及其一致性研究

一、引言发展是人类永恒的主题。但人类对于发展的认识是逐渐深化的 ,尤其是二战以后 ,其认识的深度、广度都发生了深刻的变化。一般认为 ,半个世纪以来 ,发展观大致经过了 50～ 6 0年代的“经济观”、70年代的“社会观”、70～ 80年代的“文化观”、80年代以来的“生态观”和“可持续发展观”等四个阶段。随着发展观的改变 ,衡量发展水平的尺度也逐渐变化。特别是近 2 0年中 ,新的衡量发展水平的统计尺度渐次问世并得到广泛应用 ,并对各国的社会经济统计和核算体系产生着重大影响。这些尺度之间到底有什么关系 ?是否如有些人认为的那样是“…     

Diversity of vocabulary and homogeneity of literary style

To help settle the debate around the authorship of Tirant lo Blanc, we analyse the evolution of the diversity of the vocabulary used in that book, as measured through eight different diversity indices. The exploratory analysis reveals a clear single shift in diversity, that is estimated through change-point techniques to be in chapter 382, and might indicate the existence of one main author writing about four fifths of the book, and of a second author finishing the last one fifth of the book. Before chapter 382, the language is richer and more diverse than after it.     

MATRIX ANALYSIS OF THE CASH FLOWS AND RESERVES OF A LIFE OFFICE

Matrix projection methods have been used by demographers to prove a number of powerful general theorems concerning population growth and development. The methods have also been applied to the study of graded social systems and to problems of manpower planning. The policy-holders of a life office and the members of a superannuation fund belong to graded systems with age as the important hierarchical variable. The abovementioned methods can therefore be used to study the growth and development of the membership of these institutions.
Recent articles by Sherris (1977), and Pollard and Sherris (1979a, 1979b) have shown that matrix analysis is also very useful for projecting the cash flows and reserves of life assurance companies and superannuation funds.
In this paper the use of these methods is illustrated by the projection of the reserves of a life office writing whole-life assurance contracts. We find that as the fund matures, it grows exponentially.     

A model company

HUGIN Expert is a small company writing software that can be used to create expert systems, using probability in the guise of graphical models. Steffen Lauritzen describes his part in the genesis and development of the company.     

Score tests for independence in semiparametric competing risks models

A popular model for competing risks postulates the existence of a latent unobserved failure time for each risk. Assuming that these underlying failure times are independent is attractive since it allows standard statistical tools for right-censored lifetime data to be used in the analysis. This paper proposes simple independence score tests for the validity of this assumption when the individual risks are modeled using semiparametric proportional hazards regressions. It assumes that covariates are available, making the model identifiable. The score tests are derived for alternatives that specify that copulas are responsible for a possible dependency between the competing risks. The test statistics are constructed by adding to the partial likelihoods for the individual risks an explanatory variable for the dependency between the risks. A variance estimator is derived by writing the score function and the Fisher information matrix for the marginal models as stochastic integrals. Pitman efficiencies are used to compare test statistics. A simulation study and a numerical example illustrate the methodology proposed in this paper.     

Web‐based resources to assist the statistical analysis and presentation of data

The intention of this article is to highlight sources of web‐based reference material, courses and software that will aid statisticians and researchers. The article includes websites that: assist in writing a protocol or proposal; link to online statistical textbooks; and provide statistical calculators or links to free statistical software and other guidance documents. Copyright © 2005 John Wiley & Sons, Ltd.     

Writing Technical Papers or Reports

Five rules that help to improve technical writing are (1) Start at the end; (2) Be prepared to revise; (3) Cut down on long words; (4) Be brief; (5) Think of the reader.     

Power analysis for clustered non-continuous responses in multicenter trials

Power analysis for multi-center randomized control trials is quite difficult to perform for non-continuous responses when site differences are modeled by random effects using the generalized linear mixed-effects model (GLMM). First, it is not possible to construct power functions analytically, because of the extreme complexity of the sampling distribution of parameter estimates. Second, Monte Carlo (MC) simulation, a popular option for estimating power for complex models, does not work within the current context because of a lack of methods and software packages that would provide reliable estimates for fitting such GLMMs. For example, even statistical packages from software giants like SAS do not provide reliable estimates at the time of writing. Another major limitation of MC simulation is the lengthy running time, especially for complex models such as GLMM, especially when estimating power for multiple scenarios of interest. We present a new approach to address such limitations. The proposed approach defines a marginal model to approximate the GLMM and estimates power without relying on MC simulation. The approach is illustrated with both real and simulated data, with the simulation study demonstrating good performance of the method.     

Do the left-handed die young?

Martin Bland and Doug Altman have been writing together for nearly 30 years, much of it about the consequences of misleading statistical analyses. In what they estimate to be their 79th publication, they comment on a long-running controversy: do left-handed people have shorter lives than the right-handed?     

The truth about those little red lights: a tale of power and poppycock

Leaving your electrical appliances on standby wastes-how much? Up to 10% of the electricity supply. Everyone knows that. Or is it 8%? Or 3%? Anyway, it is a lot, and the statistic has acquired a life of its own. Matthew Parris's article from The Times of July 22nd, 2006, was runner-up in the 2007 Royal Statistical Society competition for journalists writing on a statistical theme. The Chancellor he refers to, one Gordon Brown, is now, of course, the Prime Minister.     

A note on current methods of partitioning the contigency x2 statistic

Comparisons are made between the two values of the chisquare statistic in three dimensional contigency tables as defined respectively by the ‘multiplicative’ an ‘additive’ models of zero second order interaction. It is shown that in practice the two definitions frequently give comparable values for the statistics, and it is concluded that interaction measures, and paritioning of the overall association chisuare, are more useful than the considerable writing on the models' deficiencies would seem to indicate. There seems to be a slight bias in favour of the multiplicative model.     

Business and industrial statistics: the early years

Before his death in July 2002, George Barnard had started writing a sketch of the history of business and industrial statistics in the first 50 years of the twentieth century. The piece was never finished, but it is nonetheless a valuable memoir of the early development of the discipline, from someone who knew those involved.     

Fishery and Forestry Management

There are a large number of different definitions used for sample quantiles in statistical computer packages. Often within the same package one definition will be used to compute a quantile explicitly, while other definitions may be used when producing a boxplot, a probability plot, or a QQ plot. We compare the most commonly implemented sample quantile definitions by writing them in a common notation and investigating their motivation and some of their properties. We argue that there is a need to adopt a standard definition for sample quantiles so that the same answers are produced by different packages and within each package. We conclude by recommending that the median-unbiased estimator be used because it has most of the desirable properties of a quantile estimator and can be defined independently of the underlying distribution.     

Copulas Constructed from Horizontal Sections

In analogy with the study of copulas whose diagonal sections have been fixed, we study the set _h of copulas for which a horizontal section h has been given. We first show that this set is not empty, by explicitly writing one such copula, which we call horizontal copula. Then we find the copulas that bound both below and above the set _h. Finally, we determine the expressions for Kendall's tau and Spearman's rho for the horizontal and the bounding copulas.     

Discipline-Specific Literature Bases: A View of the APS Model

Abstract

Librarians see the large quantities of literature and the complete writing/publishing/world as a complete system. Changes to one piece (e.g., making publishing or reading electronic) will not fundamentally change the process. The pieces of the system are there, not for technological reasons, but for reasons of authority, validation, and self-correction in the process of scholarly communication. Electronic publishing will cause great changes, but the changes will not eliminate roles that now exist. The changes will be to enhance our abilities to better do that which we do now, whether that be to edit, review, referee, write, or manage the information flow.     

Using categorical markers as auxiliary variables in log‐rank tests and hazard ratio estimation

Markers, which are prognostic longitudinal variables, can be used to replace some of the information lost due to right censoring. They may also be used to remove or reduce bias due to informative censoring. In this paper, the authors propose novel methods for using markers to increase the efficiency of log‐rank tests and hazard ratio estimation, as well as parametric estimation. They propose a «plug‐in» methodology that consists of writing the test statistic or estimate of interest as a functional of Kaplan–Meier estimators. The latter are then replaced by an efficient estimator of the survival curve that incorporates information from markers. Using simulations, the authors show that the resulting estimators and tests can be up to 30% more efficient than the usual procedures, provided that the marker is highly prognostic and that the frequency of censoring is high.     

The table auto-regressive moving-average model for (categorical) stationary series: statistical properties (causality; from the all random to the conditional random)

A strictly stationary time series is modelled directly, once the variables' realizations fit into a table: no knowledge of a distribution is required other than the prior discretization. A multiplicative model with combined random ‘Auto-Regressive’ and ‘Moving-Average’ parts is considered for the serial dependence. Based on a multi-sequence of unobserved series that serve as differences and differences of differences from the main building block, a causal version is obtained; a condition that secures an exponential rate of convergence for its expected random coefficients is presented. For the remainder, writing the conditional probability as a function of past conditional probabilities, is within reach: subject to the presence of the moving-average segment in the original equation, what could be a long process of elimination with mathematical arguments concludes with a new derivation that does not support a simplistic linear dependence on the lagged probability values.     

Improved variance bounds for unbiased estimation in inverse sampling

Sathe (1977) derived sharper variance bounds for inverse sample unbiased estimator of the negative binomial parameter p. In the present writing improved upper/lower variance bounds are achieved and the relative improvement is numerically illustrated.