Even You Can Learn Statistics This page intentionally left blank Even You Can Learn Statistics A Guide for Everyone Who Has Ever Been Afraid of Statistics David M. Levine, Ph.D. David F. Stephan PEARSON PRENTICE HALL An Imprint of PEARSON EDUCATION Upper Saddle River, NJ • New York • London • San Francisco • Toronto Sydney • Tokyo • Singapore • Hong Kong Cape Town • Madrid • Paris • Milan • Munich • Amsterdam www.ft-ph.com Library of Congress Catalog-in-Publication: 2004107420 Executive Editor: Jim Boyd Editorial Assistant: Richard Winkler Marketing Manager: Martin Litkowski International Marketing Manager: Tim Galligan Managing Editor: Gina Kanouse Project Editor:Kayla Dugger Design Manager:Sandra Schroeder Cover Designers: Alan Clements andGary Adair Composition and Interior Design:Argosy and Jake McFarland Manufacturing Buyer: Dan Uhrig 2005 Pearson Education, Inc. Publishing as Pearson Prentice Hall Upper Saddle River, NJ 07458 Prentice Hall offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales. For more information, please contact: U.S. Corporate and Government Sales, 1-800-382-3419, [email protected]. For sales outside of the U.S., please contact: International Sales, 1-317-581-3793, [email protected]. Company and product names mentioned herein are the trademarks or registered trademarks of their respective owners. All rights reserved. No part of this book may be reproduced, in any form or by any means, without permission in writing from the publisher. Printed in the United States of America 1stPrinting ISBN 0-13-146757-3 Pearson Education Ltd. Pearson Education Australia Pty., Limited Pearson Education Singapore, Pte. Ltd. Pearson Education North Asia Ltd. Pearson Education Canada, Ltd. Pearson Educación de Mexico, S.A. de C.V. Pearson Education—Japan Pearson Education Malaysia, Pte. Ltd. To our wives Marilyn and Mary To our children Sharyn and Mark And to our parents in loving memory, Lee, Reuben, and Francis in honor, Ruth This page intentionally left blank vii TABLE OF CONTENTS Table of Contents Introduction xvii Chapter 1 Fundamentals of Statistics 1 1.1 The Five Basic Words of Statistics 2 Population 2 Sample 2 Parameter 2 Statistic 3 Variable 3 1.2 The Branches of Statistics 4 Descriptive Statistics 4 Inferential Statistics 5 1.3 Sources of Data 5 Published Sources 5 Experiments 6 Surveys 6 1.4 Sampling Concepts 7 Sampling 7 Probability Sampling 7 Simple Random Sampling 7 Frame 8 1.5 Sample Selection Methods 8 Sampling With Replacement 8 Sampling Without Replacement 8 One-Minute Summary 10 Test Yourself 11 Answers to Test Yourself Questions 14 References 14 Chapter 2 Presenting Data in Charts and Tables 17 2.1 Presenting Categorical Data 17 The Summary Table 17 The Bar Chart 18 The Pie Chart 19 The Pareto Diagram 20 viii TABLE OF CONTENTS Two-Way Cross-Classification Tables 22 2.2 Presenting Numerical Data 24 The Frequency and Percentage Distribution 24 Histogram 25 The Dot Scale Diagram 27 The Time-Series Plot 28 The Scatter Plot 28 2.3 Misusing Graphs 30 One-Minute Summary 32 Test Yourself 32 Answers to Test Yourself Questions 35 References 36 Chapter 3 Descriptive Statistics for Numerical Variables 37 3.1 Measures of Central Tendency 37 The Mean 37 The Median 40 The Mode 41 Quartiles 41 3.2 Measures of Variation 45 The Range 45 The Variance and the Standard Deviation 46 Standard (Z) Scores 49 3.3 Shape of Distributions 50 Symmetrical Shape 50 Left-Skewed Shape 50 Right-Skewed Shape 51 The Box-and-Whisker Plot 52 Important Equations 56 One-Minute Summary 56 Test Yourself 57 Answers to Test Yourself Questions 59 References 60 Chapter 4 Probability 61 4.1 Getting Started with Probability 61 Event 61 Elementary Event 62 ix TABLE OF CONTENTS Random Variable 62 Probability 62 Collectively Exhaustive Events 64 4.2 Some Rules of Probability 64 4.3 Assigning Probabilities 67 Classical Approach 67 Empirical Approach 67 Subjective Approach 68 One-Minute Summary 68 Test Yourself 68 Answers to Test Yourself Questions 70 References 70 Chapter 5 Probability Distributions 73 5.1 Probability Distributions for Discrete Variables 73 Discrete Probability Distribution 73 The Expected Value of a Random Variable 75 Standard Deviation of a Random Variable ((cid:1)) 76 5.2 The Binomial and Poisson Probability Distributions 79 The Binomial Distribution 79 The Poisson Distribution 83 5.3 Continuous Probability Distributions and the Normal Distribution 87 Normal Distribution 87 Using Standard Deviation Units 89 Finding the ZValue from the Area Under the Normal Curve 91 5.4 The Normal Probability Plot 94 Important Equations 96 One-Minute Summary 96 Test Yourself 97 Answers to Test Yourself Questions 101 References 102 Chapter 6 Sampling Distributions and Confidence Intervals 103 6.1 Sampling Distributions 104 Sampling Distribution 104 Sampling Distribution of the Mean and the Central Limit Theorem 104