ESSENTIALS OF
BIOSTATISTICSFOR UNDERGRADUATE, POSTGRADUATE STUDENTS OF
MEDICAL SCIENCE, BIOMEDICAL SCIENCES AND RESEARCHERS
Indranil SahaAssociate Professor
Department of Community MedicineESI PGIMSR & ESIC Medical College, Kolkata
Bobby PaulAssistant Professor
Department of Preventive and Social Medicine,All India Institute of Hygiene and Public Health, Kolkata
ACADEMIC PUBLISHERSKOLKATA-700 073
E-mail : [email protected] : www.academicpublishers.in
© Reserved
First Published April 2010Second Edition July 2016
ISBN : 978-93-83420-71-1
Price : Rupees two hundred only.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, ortransmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without theprior permission of the copyright holders.
Published by B. K. Dhur of Academic Publishers, 5A, Bhawani Dutta Lane, Kolkata-700 073, laser typesetting by Studio Michaelangelo, 5A, Bhawani Dutta Lane, Kolkata-700 073 and printed at Rajendra Offset,11 Panchanan Ghosh Lane, Kolkata-700 009.
Dedicated to ourparents
andchildren
Abbreviations used in this book
AIIMS : All India Institute of Medical SciencesAI : All India
AIIH&PH : All India Institute of Hygiene and Public Health
AP : Andhra Pradesh State Entrance Examination
CU : Calcutta University State Entrance Examination
DNB : Diplomate of National Board
DPH : Diploma of Public Health
IA Exam : Internal Assessment Examination of 3rd Professional MBBS Part I
IPGME&R : Institute of Post Graduate Medical Education and Research
JIPMER : Jawaharlal Nehru Institute of Postgraduate Medical Education and Research
MAHE : Manipal Medical Entrance Examination
MPH : Master of Public Health
PGI : Post Graduate Institute, Chandigarh
TN : Tamil Nadu State Entrance Examination
UPSC : Union Public Service Commission
WBUHS : West Bengal University of Health Sciences
Preface to the second edition
We welcome the readers who wish to learn biostatistics. The purpose of this book is togive a comprehensive insight into the basic aspects of biostatistics that is easy to read andrelevant with useful practical applications. Fundamental concepts are presented in a highlysuccinct format suitable for students without in depth background in mathematics or statistics.
Apart from other conventional statistical books, we have deliberately kept discussion ofstatistical theory to a minimum. We have emphasized on giving an overview of key conceptsof methods of data presentation, scales of measurement, measures of central tendency anddispersion, normal distribution, sample si1ze calculation and sampling techniques, probability,sampling variability, null hypothesis, and details on tests of significance, written in lucid language.The chapter on ‘Art and Science of Research’ provides an insight into research methodologyand study designs and the chapter on 'Publication in Journal' provides useful guidelines forpublishing one’s research work. This makes it a handbook of essentials of biostatistics forundergraduate and postgraduate students and researchers from the field of medicine, publichealth, preventive medicine, nursing, dental, psychology, paramedical sciences, biologicaland social sciences or in a nutshell, anyone who encounters the use of biostatistics in his/herrespective field. This text is also helpful for PhD students who are preparing for their examinationon research methodology as well as undergraduate and postgraduate students to prepare fortheir short research projects / thesis and writing answers on biostatistics in their final universityexamination.
The favourable response that the first edition of this book received from teachers andstudents encouraged us to write the second edition. Based on teaching experience and studentfeedback, we have transformed the question answer format of the previous book into textformat in a simplistic language with a major objective to motivate students and readers todevelop a positive attitude towards learning biostatistics. We have aimed to raise this positiveattitude by introducing the concepts through simple worked-out examples. Each chapter beginswith an introductory note, proceeds on to the details in a concise and clear manner and endswith examples of application of the statistical methods in published literature. In addition,there are exercises at the end of each chapter for the purpose of learning and practice - longquestions, short notes, justify / explain with examples, statistical and epidemiological exercisesfrom different university examinations for MBBS students as well as MD students. Multiplechoice questions from different postgraduate entrance examinations with their respective answersand explanations along with some new set of questions have also been incorporated. Thoughample study materials are available online, though in a fragmented form, it fails to provide abetter understanding of this discipline in a comprehensive manner.
We humbly submit that in spite of our laborious efforts, there may be some errors, inaccuracies,and ambiguous statements. We would appreciate receiving the comments of our valuablereaders. We have a special electronic mail account for your constructive feedback [email protected] since first edition book.
We are especially grateful to the entire team of Academic Publishers for publishing thesecond edition book.
4th June, 2016 Indranil [email protected] Bobby Paul
Preface to the first edition
Biostatistics - MCQ and Essentials has been designed especially for the MBBS studentsand postgraduate aspirants who are concentrating both on preparation for entranceexamination as well as gaining a good grip on the subject. Each chapter begins with abrief introduction of the topic, and then, instead of going into monotonous explanation,the authors have used the format of MCQ with the answers and their relevant explanationin the form of text. Thus it would be beneficial in writing questions in theory papers aswell as to face practical and oral in MBBS Part - I university examination. This book willalso be helpful for post graduate students to some extent for preparing their thesis andwriting short notes on biostatistics in their final university examination. The topics, suchas test of significance, probability, correlation, regression etc. are usually not coveredduring undergraduate teaching, but are frequenters in post graduate entrance examination.These chapters are dealt with in depth for better understanding which will help them toanswer the MCQ. Different MCQ from different examinations for the last 20 years upto2010 have been discussed along with some new set of questions. This portion is anunique feature of this book. These new sets of questions are included in almost everychapter in an attempt to include many relevant important questions that may come in future.
Thus it would be helpful for preparing MD/MS, All India, AIIMS and different stateexaminations like CU, Karnataka etc. along with DNB and UPSC examinations. Oftenresearchers are interested to know the appropriate statistical test needed to apply indifferent sets of data. Those researchers as well as students doing dissertation will bebenefitted regarding use of different statistical significance tests, which has been dealtlucidly in this book.
Suggestions, criticisms and biostatistics MCQ of different entrance examinationsfrom the readers are welcome to make the book more useful, which will be gratefullyacknowledged in future editions.
We are specially grateful to Mrs. Sandhya Paul, Mrs. Mahua Ghosh, Miss SnehaSaha, Master Rayan Saha & to the staff members of Academic Publishers for publishingthe book.
22 March, 2010
Indranil SahaBobby Paul
ACKNOWLEDGEMENT
Dr. Saswati Nandy - R. G. Kar Medical College, West Bengal Prof. Aparajita Dasgupta - All India Institute of Hygiene & Public Health, WB
Prof. Jayasri Mitra - ESI PGIMSR & ESIC Medical College, Joka, WB
Prof. Ramendra Narayan Chaudhury - All India Institute of Hygiene & Public Health, WB
Prof. Akhil Bandhu Biswas - Institute of Health and Family Welfare, Swasthya Bhawan, WB
Prof. Gautam Ghose - IQ City Medical College, Durgapur, West Bengal
Prof. Saibendu Kumar Lahiri - R. G. Kar Medical College, West Bengal
Prof. Samir Dasgupta - North Bengal Medical College, Siliguri, West Bengal
Prof. Raghunath Misra - Institute of Post Graduate Medical Education & Research, WB
Prof. Dilip Kumar Das - Burdwan Medical College, West Bengal
Prof. Rabindra Nath Sinha - All India Institute of Hygiene & Public Health, WB
Prof. Arup Kumar Kundu - IQ City, Medical College, Durgapur, West Bengal
Prof. Sarmila Mallik - Murshidabad Medical College, West Bengal
Late Prof. Ranadeb Biswas - All India Institute of Hygiene & Public Health, WB
Dr. Ashish Kumar Yadav - ESI PGIMSR & ESIC Medical College, Joka, WB
Dr. Sk. Samim Ferdows - IQ City Medical College, Durgapur, West Bengal
Dr. Rabindra Nath Roy - Burdwan Medical College, West Bengal
Dr. Sanjit Dey - Rajabazar Science College, West Bengal
Dr. Ruchi Yadav - Rural Institute of Medical Sciences, Saifai, Etawah, Uttar Pradesh
Dr. Arijit Banerjee - Eastern Coal Field, Durgapur, West Bengal
Dr. Prabha Shrivastava - Burdwan Medical College, West Bengal
Dr. Lina Bandyopadhyay - All India Institute of Hygiene & Public Health, WB
Dr. Shweta Goswami - ESI PGIMSR & ESIC Medical College, Joka, WB
Dr. Md. Abdur Rahman - Malda Medical College, West Bengal
Dr. Susmita Chaudhuri - ESI PGIMSR & ESIC Medical College, Joka, WB
Dr. Sarbajit Ray - Institute of Post Graduate Medical Education & Research, WB
Dr. Md. Mehboob Ulislam - Burdwan Medical College, West Bengal
Mr. Sudip Karmakar - IQ City Medical College, Durgapur, West Bengal
CONTENTS
Chapter 1 : DATA AND ITS PRESENTATION 1-28Introduction 1; Introduction to some common terminology used in statistics 1; Classification of data2; Presentation of data 4; Applications 18; Exercises 19; Answers 24.
Chapter 2 : DIFFERENT SCALES OF MEASUREMENTS 29-35Introduction 29; Different scales of measurement 29; Some specific scales 31; Applications 33;Exercises 34; Answers 35.
Chapter 3 : CENTRAL TENDENCY 36-42Introduction 36; Concept of central tendency 36; Exercises 39; Answers 41.
Chapter 4 : NORMAL DISTRIBUTION AND MEASURES OF DISPERSION 43-62Introduction 43; Measures of location 43; Normal curve 44; Skewness 45; Kurtosis 46; Z score 47;Standard normal curve 48; Measures of dispersions/variations 49; Different types of distribution52; Application 53; Exercises 53; Answers 59.
Chapter 5 : SAMPLE SIZE AND SAMPLING TECHNIQUE 63-78Introduction 63; Some common terminology used in sampling 63; Sample size calculation 64;Sampling technique 66; Sampling bias 74; Design effect 74; Exercises 74; Answers 77.
Chapter 6 : PROBABILITY 79-84Introduction 79; Probability 79; P value 81; Exercises 82; Answers 84.
Chapter 7 : SAMPLING VARIABILITY AND NULL HYPOTHESIS 85-94Introduction 85; Standard error (SE) 85; Tests of significance applying standard error 86; Nullhypothesis 87; Sampling error 88; Exercises 89; Answers 93.
Chapter 8 : DIFFERENCE BETWEEN PROPORTIONS 95-106Introduction 95; Chi-square test (Pearson’s chi-square test) 95; Assumptions for pearson’schi-square test 96; General procedure of chi-square test 96; Different variants of chi-square test97; Contingency table 100; Degrees of freedom (df) 100; Effect size in chi-square test 100; Z testfor proportion 101; Cochran-armitage trend test 101; Test of significance 102; Applications 102;Exercises 103; Answers 105.
Chapter 9 : DIFFERENCE BETWEEN MEANS 107-122Introduction 107; While choosing a statistical test, following statements are taken into consideration 107;Tests relating to comparison of means 107; Z test for mean 108; Student’s t test 108; Mann-whitneyu test 111; Wilcoxon matched-pairs signed rank test 111; ANOVA / Analysis of variance 112;Friedman’s ANOVA by rank 114; Kruskal-wallis h test 115; MANOVA / Multivariate analysis ofvariance 115; Analysis of co-variance (ANCOVA) 116; Effect size 116; Applications 117;Exercises 117; Answers 121.
Chapter 10 : CORRELATION 123-132Introduction 123; Correlation 123; Interpretation of correlation 124; Correlation coefficient to beused 125; Assumptions for correlation 125; Output of correlation 125; Correlation for nominal scaledata 126; Correlation for ordinal scale data 126; Correlation for interval and ratio scale data 127;Universal relationship 127; Correlation matrix 127; Some other types of correlation 127;Applications 129; Exercises 129; Answers 132.
Chapter 11 : REGRESSION 133-140Introduction 133; Regression 133; Types of regression analysis 133; Linear regression 134; Logisticregression 136; Cox regression model 138; Multivariable model versus univariate / bivariate model138; Applications 139; Exercises 139; Answers 140.
Chapter 12 : ART AND SCIENCE OF RESEARCH 141-177Introduction 141; Some commonly used definitions 141; Research protocol 142; Cardinal steps ofpreparing a protocol 143; Primary data 144; Secondary data 149; Ethical issues 149; Guidelines towrite a research report / thesis 152; Some common study designs 159; Clinical trial 163; Systematicreview 165; Meta-analysis 165; Strength and weaknesses of common study designs 167; Evidencebased medicine 168; Applications 169; Exercises 170; Answers 174.
Chapter 13 : PUBLICATION IN JOURNAL 178-181Introduction 178; Manuscript preparation 178; Sections of the submitted manuscript 178; Someuseful terminologies 180.
APPENDIX 182-186
REFERRENCE 187-188
INDEX 189-190
IMPORTANT DAYS 191-192
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