Changes and updates in this edition:1. All chapters have been thoroughly revised and edited.2. Basic concepts have been clearly explained in all the chapters.3. All data have been updated based on Census 2011 and SRS 2017, and all other latest available sources.4. Many examples have been modified to be applicable in the present context. However, most of the solved examples have been kept as in previous editions, along with the original reference to the author?s own work done.5. New subtopics have been added and covered in detail in many chapters, as follows:Chapter 2: Methods of collection of medical data and the tools used for the purpose, have been explained in detail for both quantitative and qualitative dataChapter 6: Determination of sample size and nonprobability sampling techniques have been explained.Chapter 7: Commonly used terms in probability have been listed and defined.Chapter 8: Types and steps of tests of significance have been discussed. Choice of test of significance for different situations, according to type of data involved has been explained simply in the form of tables.Chapter 13: Hierarchy of epidemiological research studies has been discussed in detail.Chapter 15: All tables have been revised and some tables added, based on most recent data, i.e. Census 2011 and SRS 2017.Chapter 19: Basics of Excel have been explained. Logistic regression analysis using SPSS has been discussed in detail