MONOGRAPHS ON APPLIED PROBABILITY AND STATISTICS General Editors M.S. BARTLETT, F.R.S. andD.R. COX, F.R.S. SOME BASIC THEORY FOR STATISTICAL INFERENCE Some Basic Theory for Statistical Inference E.J.G. PITMAN M.A. D.Sc. F.A.A. Emeritus Professor ofM athematics University ofTasmania LONDON CHAPMAN AND HALL Boca Raton London New York A Halsted Press Book CRC Press is an imprint of the JOHNT ayWlor I&L FEranYcis G&ro upS, aOn NinSfo,r mNa EbuWsines sYORK First published 1979 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 Reissued 2018 by CRC Press © 1979 E.J.G. Pitman CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works This book contains information obtained from authentic and highly regarded sources. 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Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging in Publication Data Pitman, Edwin J. G. Some basic theory for statistical inference. (Monographs on applied probability and statistics) Includes bibliographical references. 1. Mathematical statistics. I. Title. QA276.P537 519.5 78-11921 ISBN 0–470–26554–X A Library of Congress record exists under LC control number: 78011921 Publisher’s Note The publisher has gone to great lengths to ensure the quality of this reprint but points out that some imper- fections in the original copies may be apparent. Disclaimer The publisher has made every effort to trace copyright holders and welcomes correspondence from those they have been unable to contact. ISBN 13: 978-1-315-89767-7 (hbk) ISBN 13: 978-1-351-07677-7 (ebk) Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com CONTENTS Preface page vii Chapter one 1 Basic Principles of the Theory of Inference, The Likelihood Principle, Sufficient Statistics Chapter two 6 Distance between Probability Measures Chapter three 11 Sensitivity of a Family of Probability Measures with respect to a Parameter Chapter Jour 24 Sensitivity Rating, Conditional Sensitivity, The Discrimination Rate Statistic Chapter five 29 Efficacy, Sensitivity, The Cramer-Rao Inequality Chapter six 50 Many Parameters, The Sensitivity Matrix Chapter seven 56 Asymptotic Power of a Test, Asymptotic Relative Efficiency Chapter eight 63 Maximum Likelihood Estimation Chapter nine 79 The Sample Distribution Function Appendix: Mathematical Preliminaries 98 References 107 Index 109 v PREFACE This book is largely based on work done in 1973 while I was a Senior Visiting Research Fellow, supported by the Science Research Council, in the Mathematics Department of Dundee University, and later while a visitor in the Department of Statistics at the University of Melbourne. In both institutions, and also at the 1975 Summer Research Institute of the Australian Mathe- matical Society, I gave a series of talks with the general title 'A New Look at Some Old Statistical Theory'. That title indicates fairly well my intentions when I started writing this book. I was encouraged in my project by some remarks of Professor D.V. Lindley (1972) in his review of The Theory of Statistical Inference by S. Zacks: One point that does distress me about this book-and let me hasten to say that this is not the fault of the author-is the ugliness of some of the material and the drabness of most of it ... The truth is that the mathematics of our subject has little beauty to it. Is it wrong to ask that a subject should be a delight for its own sake? I hope not. Is there no elegant proof of the consistency of maximum likelihood, or do we have to live with inelegant conditions? I share Lindley's dissatisfaction with much statistical theory. This book is an attempt to present some of the basic mathematical results required for statistical inference with some elegance as well as precision, and at a level which will make it readable by most students of statistics. The topics treated are simply those that I have been able to do to my own satisfaction by this date. I am grateful to those who, at Dundee, Melbourne, or Sydney, were presented with earlier versions, and who helped with their questions and criticisms. I am specially grateful to Professor E.J. Williams, with whom I have had many discussions, and who arranged for and supervised the typing; to Judith Adams and Judith Benney, who did most ofthe typing, and to Betty La by, who drew the diagrams. E.J.G.P. vii CHAPTER ONE BASIC PRINCIPLES OF THE THEORY OF INFERENCE THE LIKELIHOOD PRINCIPLE SUFFICIENT STATISTICS In developing the theory of statistical inference, I find it helpful to bear in mind two considerations. Firstly, I take the view that the aim of the theory of inference is to provide a set of principles, which help the statistician to assess the strength of the evidence supplied by a trial or experiment for or against a hypothesis, or to assess the reliability of an estimate derived from the result of such a trial or experiment. In making such an assessment we may look at the results to be assessed from various points of view, and express ourselves in various ways. For example, we may think and speak in terms of repeated trials as for confi- dence limits or for significance tests, or we may consider the effect of various loss functions. Standard errors do give us some comprehension of reliability; but we may sometimes prefer to think in terms of prior and posterior distributions. All of these may be helpful, and none should be interdicted. The theory of inference is persuasive rather than coercive. Secondly, statistics being essentially a branch of applied mathematics, we should be guided in our choice of principles and methods by the practical applications. All actual sample spaces are discrete, and all observable random variables have discrete distributions. The continuous distribution is a mathe- matical construction, suitable for mathematical treatment, but not practically observable. We develop our fundamental concepts, principles and methods, in the study of discrete distributions. In the case of a discrete sample space, it is easy to understand and appreciate the practical or experimental significance and value of conditional distributions, the likelihood principle, the principles of sufficiency and conditionality, and the method of maximum likelihood. These are then extended to more general distributions by means of suitable definitions and mathematical theorems.
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