Covariance Analysis for Split-Plot and Split-Block Designs

Commentaries are informative essays dealing with viewpoints of statistical practice, statistical education, and other topics considered to be of general interest to the broad readership of The American Statistician. Commentaries are similar in spirit to Letters to the Editor, but they involve longer discussions of background, issues, and perspectives. All commentaries will be refereed for their merit and compatibility with these criteria.

Proper methodology for the analysis of covariance for experiments designed in a split-plot or split-block design is not found in the statistical literature. Analyses for these designs are often performed incompletely or even incorrectly. This is especially true when popular statistical computer software packages are used for the analysis of these designs. This article provides several appropriate models, ANOVA tables, and standard errors for comparisons from experiments arranged in a standard split-plot, split–split-plot, or split-block design where a covariate has been measured on the smallest size experimental unit.     

Statistical Computing Software Reviews

This department includes the two sections New Developments in Statistical Computing and Statistical Computing Software Reviews; suitable contents for each of these sections is described under the respective section heading. Articles submitted for the department, outside the two sections, should not be highly technical and should be relevant to the teaching or practice of statistical computing.

This section is similar in organization to a Book Review section in other journals; however, software of interest to statisticians is the subject of review here. Emphasis is on software for microcomputers. Programs that operate only in larger mainframe computers will seldom receive review. Normally, producers of programs make a copy of their product available to the Section Editor, who then selects one or more persons to test the product and prepare a review.

Producers of computer software who wish to have their product reviewed are invited to contact the Section Editor, Professor Kenneth Berk, Department of Mathematics, 313 Stevenson Hall, Illinois State University, Normal, IL 61761.

Findings and opinions expressed in every review are solely those of the author. They should not be construed as reflecting endorsement of the product, or opinions held, by the American Statistical Association, nor is any warranty implied about any product reviewed.

SYSTAT Leland Wilkinson. Available from Systat, Inc., 603 Main St., Evanston, IL 60202. $495 (multiple copy and site fees available). Reviewed by Mark I. Scherwish

AIDA, Version 9/82 David A. Lingwood, Available from Action-Research Northwest, 11442 Marine View Drive, S.W., Seattle, WA 98146. $235. Reviewed by Walter Liggett

MSUSTAT, MS/PC-DOS and CP/M-80 Version 2.20 Richard E. Lund. Available from Research and Development, Inc., Montana State University, Bozeman, MT 59717–0002. $187.50 (university and multiple-copy discounts available). Reviewed by Mervyn G. Marasinghe     

Chinese American Newspapers and Periodicals in the United States and Their Web Presence

Abstract

This article presents an analysis of the Web presence of Chinese American newspapers and periodicals in the United States based on the author's last ten-year national survey of Chinese American newspapers and periodicals in the United States in 1997. The author reports on and updates the changes, development, variety, and status of Chinese American newspapers and periodicals and their Web editions. These publications and their Web presence have played a major role in maintaining the identity, cohesiveness, and structure of Chinese communities. They are the major sources for covering significant aspects of Chinese culture, including the historical, social, economic, and political development of Chinese Americans in the United States. Serials Review 2003; 29:179–198.     

Letters to the Editor

Letters to the Editor will be confined to discussions of papers which have appeared in The American Statistician and of important issues facing the statistical community. Letters discussing papers in The American Statistician must be received within two months of publication of the paper; the author of the paper will then be given an opportunity to reply and the letters and reply will be published together. All letters to the Editor will be refereed. Corrections of errors which have been noted in papers published in The American Statistician will be listed in Corrigenda at the end of this section.     

Statistical Computing Software Reviews

This section is similar in organization to a Book Review section in other journals; however, software of interest to statisticians is the subject of review here. Emphasis is on software for microcomputers. Programs that operate only in larger mainframe computers will seldom receive review. Normally, producers of programs make a copy of their product available to the Section Editor, who then selects one or more persons to test the product and prepare a review.

Producers of computer software who wish to have their product reviewed are invited to contact the Section Editor, Professor Kenneth Berk, Department of Mathematics, 313 Stevenson Hall, Illinois State University, Normal, IL 61761.

Findings and opinions expressed in every review are solely those of the author. They should not be construed as reflecting endorsement of the product, or opinions held, by the American Statistical Association, nor is any warranty implied about any product reviewed.

STAN, Version II.0. David M. Allen. Available from Statistical Consultants, Inc., 462 E. High Street, Lexington, KY 40508. $300. Reviewed by Peter A. Lachenbruch     

On the computation of the noncentral <Emphasis Type="Italic">F</Emphasis> and noncentral beta distribution

Unfortunately many of the numerous algorithms for computing the comulative distribution function (cdf) and noncentrality parameter of the noncentral F and beta distributions can produce completely incorrect results as demonstrated in the paper by examples. Existing algorithms are scrutinized and those parts that involve numerical difficulties are identified. As a result, a pseudo code is presented in which all the known numerical problems are resolved. This pseudo code can be easily implemented in programming language C or FORTRAN without understanding the complicated mathematical background. Symbolic evaluation of a finite and closed formula is proposed to compute exact cdf values. This approach makes it possible to check quickly and reliably the values returned by professional statistical packages over an extraordinarily wide parameter range without any programming knowledge. This research was motivated by the fact that a very useful table for calculating the size of detectable effects for ANOVA tables contains suspect values in the region of large noncentrality parameter values compared to the values obtained by Patnaik’s 2-moment central-F approximation. The cause is identified and the corrected form of the table for ANOVA purposes is given. The accuracy of the approximations to the noncentral-F distribution is also discussed. The authors wish to thank Mr. Richárd Király for his preliminary work. The authors are grateful to the Editor and Associate Editor of STCO and the unknown reviewers for their helpful suggestions.     

The Religion of Statistics as Practiced in Medical Journals

Commentaries are informative essays dealing with viewpoints of statistical practice, statistical education, and other topics considered to be of general interest to the broad readership of The American Statistician. Commentaries are similar in spirit to Letters to the Editor, but they involve longer discussions of background, issues, and perspectives. All commentaries will be refereed for their merit and compatibility with these criteria.

The way in which hypothesis tests are often used as the sole tool of statistics in medical research is satirized. This is followed by a suggestion for reform.     

A Graphical Display of Large Correlation Matrices

This department includes the two sections New Development in Statistical Computing and Statistical Computing Software Reviews; suitable contents for each of these sections are described under the respective section heading. Articles submitted for the department, outside the two sections, should not be highly technical and should be relevant to the teaching or practice of statistical computing.

Large correlation matrices are hard to look at. In this article we present correlations as elliptical glyphs for a simple intuitive display of large matrices.     

Report of the Ad Hoc Committee on Statistical Standards

Secretary's Note: At the meeting of the incoming Board and Council of December 29, 1952, the Committee on Committees submitted for consideration an outline regarding the tasks that should be undertaken by the Commission on Statistical Standards and Organization. The Board authorized President Cochran to appoint an ad hoc committee to explore the functions as outlined by the Committee on Committees. The ad hoc committee, under the chairmanship of Rensis Likert, Institute for Social Research, University of Michigan, has prepared an excellent report on this subject which should be the concern of all members of the Association.

The whole problem of standards in the statistical profession is a great and difficult one. The Board has authorized the publication of the ad hoc committee's report in The American Statistician in the hope that the members of the Association will submit their views regarding both the Report and the problem of standards. The entire ASA membership is invited to forward their thoughts and comments to the Office of the Secretary of the Association for possible publication in The American Statistician.     

CORAL User Group Meeting at NC Serials 2019

Abstract

This article reports on the CORAL User Group meeting at the NC Serials 2019 conference. This was the first CORAL user group meeting to take place at the NC Serials conference. The speakers provided updates from CORAL committees and highlighted new features in the most recent CORAL release. They also shared how CORAL has been used in NC State University Libraries and East Carolina University to support their e-resource workflow management.     

Accent on Teaching Materials

This department includes the two sections New Developments in Statistical Computing and Statistical Computing Software Reviews; suitable contents for each of these sections are described under the respective section heading. Articles submitted for the department, outside the two sections, should not be highly technical and should be relevant to the teaching or practice of statistical computing.

An unbiased estimator of e is used to motivate a simple simulation exercise that requires only observations from the distribution uniform on (0, 1). Antithetic variables are introduced and applied to the simulation problem to give a second unbiased estimator of e with reduced variance.     

Urban Mortgage Loan Statistics in One Life Company

For much of 1970 and during the early part of 1971 some forty members of the American Statistical Association, working as seven task force groups under the guidance of a special Steering Committee, gave much time and thought to an examination of the objectives and activities of ASA. Their purpose was to try to determine what those objectives should be and how best to accomplish them. After careful review and study by the Board of ASA, the task force and steering committee findings and recommendations were adopted, modified or supplemented and issued as an integrated Board report under the title of A Study of Future Goals of ASA.     

Papers That Evaluate Computer Programs

Commentaries are informative essays dealing with viewpoints of statistical practice, statistical education, and other topics considered to be of general interest to the broad readership of The American Statistician. Commentaries are similar in spirit to Letters to the Editor, but they involve longer discussions of background, issues, and perspectives. All commentaries will be refereed for their merit and compatibility with these criteria.     

An Examination of Discrepancies in Multiple Imputation Procedures Between SAS® and SPSS®

Multiple imputation (MI) has become a feasible method to replace missing data due to the rapid development of computer technology over the past three decades. Nonetheless, a unique issue with MI hinges on the fact that different software packages can give different results. Even when one begins with the same random number seed, conflicting findings can be obtained from the same data under an identical imputation model between SAS® and SPSS®. Consequently, as illustrated in this article, a predictor variable can be claimed both significant and not significant depending on the software being used. Based on the considerations of multiple imputation steps, including result pooling, default selection, and different numbers of imputations, practical suggestions are provided to minimize the discrepancies in the results obtained when using MI. Features of Stata® are briefly reviewed in the Discussion section to broaden the comparison of MI computing across widely used software packages.     

A formula for Type III sums of squares

Abstract

Type III methods were introduced by SAS to address difficulties in dummy-variable models for effects of multiple factors and covariates. They are widely used in practice; they are the default method in several statistical computing packages. Type III sums of squares (SSs) are defined by a set of instructions; an explicit mathematical formulation does not seem to exist.

An explicit formulation is derived in this paper. It is used to illustrate Type III SSs and to establish their properties in the two-factor ANOVA model.     

Probability scoring for spelling correction

This paper describes a new program, CORRECT, which takes words rejected by the Unix^® SPELL program, proposes a list of candidate corrections, and sorts them by probability score. The probability scores are the novel contribution of this work. They are based on a noisy channel model. It is assumed that the typist knows what words he or she wants to type but some noise is added on the way to the keyboard (in the form of typos and spelling errors). Using a classic Bayesian argument of the kind that is popular in recognition applications, especially speech recognition (Jelinek, 1985), one can often recover the intended correction,c, from a typo,t, by finding the correctionc that maximizesPr(c) Pr(t/c). The first factor,Pr(c), is a prior model of word probabilities; the second factor,Pr(t/c), is a model of the noisy channel that accounts for spelling transformations on letter sequences (insertions, deletions, substitutions and reversals). Both sets of probabilities were estimated using data collected from the Associated Press (AP) newswire over 1988 and 1989 as a training set. The AP generates about 1 million words and 500 typos per week.In evaluating the program, we found that human judges were extremely reluctant to cast a vote given only the information available to the program, and that they were much more comfortable when they could see a concordance line or two. The second half of this paper discusses some very simple methods of modeling the context usingn-gram statistics. Althoughn-gram methods are much too simple (compared with much more sophisticated methods used in artificial intelligence and natural language processing), we have found that even these very simple methods illustrate some very interesting estimation problems that will almost certainly come up when we consider more sophisticated models of contexts. The problem is how to estimate the probability of a context that we have not seen. We compare several estimation techniques and find that some are useless. Fortunately, we have found that the Good-Turing method provides an estimate of contextual probabilities that produces a significant improvement in program performance. Context is helpful in this application, but only if it is estimated very carefully.At this point, we have a number of different knowledge sources—the prior, the channel and the context—and there will certainly be more in the future. In general, performance will be improved as more and more knowledge sources are added to the system, as long as each additional knowledge source provides some new (independent) information. As we shall see, it is important to think more carefully about combination rules, especially when there are a large number of different knowledge sources.     

Preventive replacement policies with products update announcements

Abstract

When we consider the improvement of the functional performances that are released by the new updates of the products, it is an interesting problem to revisit the existing replacement policies. For such a viewpoint, four replacement models with product update announcements, i.e., PUA for abbreviation, are given in this paper: Model 1, the unit is replaced at time T or at PUA over time T. Model 2, the unit is replaced at the Kth failure or at PUA over the Kth failure. By considering both time T and failure K, Models 3 and 4 are obtained based on the approaches of replacement first and last. We obtain the expected cost rates for four models and discuss analytically their optimal replacement policies Further, numerical examples are given when the time for PUA has an exponential distribution.     

An Interview with David Baker,Poet and Editor at the Kenyon Review

Abstract

Alan May interviews David Baker, Poetry Editor of The Kenyon Review and author of 12 books of poetry (Baker’s most recent, Swift: New and Selected Poems, will be published by W.W. Norton & Co. in April). Baker discusses his work with Quarterly West, The Kenyon Review, and Kenyon Review Online. The interview also addresses the advent of online poetry, the explosion of creative writing programs, and some aspects of the history of The Kenyon Review and Quarterly West.