STATISTICS AND YOU

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What Lies ahead in This Book

This isn’t a book about the tools of statistics. It is a book about statistical ideas and their impact on everyday life, public policy, and many different fields of study. You will learn some tools, of course. Life will be easier if you have in hand a calculator with built-in statistical functions. Specifically, you need a calculator that will find means, standard deviations, and correlations. Look for a calculator that claims to do “two-variable statistics” or mentions “correlation.” If you have access to a computer with statistical software, so much the better. On the other hand, you need little formal mathematics. If you can read and use simple equations, you are in good shape. Be warned, however, that you will be asked to think. Thinking exercises the mind more deeply than following mathematical recipes. Statistics: Concepts and Controversies presents statistical ideas in four parts:

  1. I. Data production describes methods for producing data that can give clear answers to specific questions. Where the data come from really is important—basic concepts about how to select samples and design experiments are the most influential ideas in statistics.

  2. II. Data analysis concerns methods and strategies for exploring, organizing, and describing data using graphs and numerical summaries. You can learn to look at data intelligently even with quite simple tools.

  3. III. Probability is the language we use to describe chance, variation, and risk. Because variation is everywhere, probabilistic thinking helps separate reality from background noise.

  4. IV. Statistical inference moves beyond the data in hand to draw conclusions about some wider universe, taking into account that variation is everywhere and that conclusions are uncertain.

Ultimately, data are used to draw conclusions or make decisions. The process of reasoning from data consists of several steps that yield a case for the validity of the final conclusion. Each part of this book discusses issues that affect the quality of the steps in this process. It is easy to focus on mastering the details in each chapter and lose track of how these details contribute to the overall argument. To help you see how the individual chapters fit into the overall argument, we end each chapter with a section that we call “Link It,” which briefly describes how the contents of the chapter fit into the overall reasoning process. You will find this section within the “Statistics in Summary” section.

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Statistical ideas and tools emerged only slowly from the struggle to work with data. Two centuries ago, astronomers and surveyors faced the problem of combining many observations that, despite the greatest care, did not exactly match. Their efforts to deal with variation in their data produced some of the first statistical tools. As the social sciences emerged in the nineteenth century, old statistical ideas were transformed and new ones were invented to describe the variation in individuals and societies. The study of heredity and of variable populations in biology brought more advance. The first half of the twentieth century gave birth to statistical designs for producing data and to statistical inference based on probability. By midcentury, it was clear that a new discipline had been born. As all fields of study place more emphasis on data and increasingly recognize that variability in data is unavoidable, statistics has become a central intellectual method. Every educated person should be acquainted with statistical reasoning. Reading this book will enable you to make that acquaintance.