Principles of medical statistics

Book Review Principles of Medical Statistics, 12th Ed, by A. B. Hill and I. D. Hill, Edward Arnold, London, 1991, 339 pages, $20. The first edition of this book appeared in 1937 and has become by any standards a classic on topics in medical statistics, particularly epidemiology and clinical trials. The book has undergone many changes over this time as it has passed through to this twelfth edition. In this process the book has traveled alongside concurrent and major developments in medical statistics, medical computing, and epidemiological methods. In fact, one criticism is that the impact of the first author on establishing the randomized clinical trial as a vital tool for the assessment of alternative therapies and of the second author in the field of statistical computing are not given their due prominence. There is little reference to their own substantial contributions and this is a pity. It is a pity, too, that the foreword to the first edition by the editor of The Lancet and the accompanying preface are not reproduced in this edition. Both are pertinent to the current use and misuse of statistical methods in medicine, albeit written so long ago. The book describes in nonmathematical terms the principles of statistical methods relevant to medicine. It deals with collection, analysis, and presentation of data and the processes required to deduce causation and etiology of a disease. Pitfalls and problems associated with the presentation and interpretation of statistics are considered. There are a total of 28 chapters, 7 appendices, and 7 statistical tables. The book differs from earlier editions in that more detail is included on the normal, binomial, and Poisson distributions, Fisher's exact test, Kendall's rank correlation, and the logrank test. For readers of this journal there will be some disappointment that clinical trials are given so little prominence. However, the 28 pages of Chapter 23 discuss topics that are all of direct relevance to those concerned with the dayto-day running of clinical trials. This chapter has sections entitled: the ethical problem; imperfect comparisons; retrospective, or historical, controls; the aim of the controlled trial; the construction of groups; the treatment; measuring the results; reporting the results; differential exclusions; duration of treatment; the numbers required; which patients respond?; the patient as his own control; matched pairs; and the interaction of treatments. It is also useful to have the British Medical Research Council statement concerning "Responsibility in Investigations of H u m a n Subjects" and "Declaration of Helsinki" guidelines at hand (Appendix G). These make interesting reading especially in respect to the thorny question of informed consent. There is some discussion of data forms (proforma) in the context of a sample survey, but the special problems of follow-up data in clinical trials including collection, storage, and processing are not alluded to. As a trialist this is a disappointment. Controlled Clinical Trials 13:515-516 (1992) © Elsevier Science Publishing Co., Inc. 1992 655 A v e n u e of the Americas, N e w York, N e w York 10010

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Book Review There are other places where the book is disappointing. The discussion of the merits of a 2 x 2 factorial design (p. 236) leaves the reader in the air. Usually one can sum or average over each factor separately but not in the example chosen because it is unbalanced in the four (2 x 2) groups. This lack of balance will nearly always be the case in the randomized clinical trial and so the reader needs to be reminded of the distinction between this factorial situation and the one encountered (perhaps) in laboratory studies. This typifies some of the problems with the book as I see it--the level of prior understanding expected of the reader is somewhat variable. For example, the paired and unpaired t tests and their nonparametric counterparts are given only seven pages between them. This is not enough for someone who is meeting these ideas for the first time. In contrast, there is too much emphasis on the calculation of group life tables, yet no solution is offered to the "mean stay in prison" problem discussed on p. 256. In a text of this nature I would find it useful to provide a full discussion of the Kaplan-Meier product limit estimate of the survival curve. The discussion of the logrank method is far too brief. I wonder too if the details of calculation of group means, variances, and covariances are really necessary, particularly as the authors point out the availability of computer packages for "statistical" analysis. There has been some debate, in the discussion following the paper by Altman and Bland (1991), by the second author of this book in relation to whether examples using ficticious data are useful. The current, dare I say majority, opinion is that real should conquer fictitious. This is clearly not the view of Hill and Hill. Who should read the book? Clearly everyone involved with the use (and abuse) of statistics in medicine, particularly clinical trials and epidemiology. Those concerned with clinical trials would benefit from a reading of Chapter 23. It should not be the first book to read for those approaching the special problems of medical statistics from a clinical or statistical perspective for the first time. However, I did enjoy reading this book. It is well written, albeit the style is somewhat British (and no worse for that!), and it contains plenty of good common sense advice. It is a book that should be on the shelf of every clinical trialist. David Machin MRC Cancer Trials Office 1 Brooklands Avenue Cambridge CB2 2BB United Kingdom

Reference

Altman DG, Bland JM: Improving doctors' understanding of statistics (with discussion). J Roy Stat Soc A 154:223-267, 1991