Introduction

So you’ve gone through some of the basics of statistics. Means, medians, and standard deviations all ring a bell. You know about surveys and experiments and the basic ideas of correlation and simple regression. You’ve studied probability, margin of error, and a few hypothesis tests and confidence intervals. Are you ready to load your statistical toolbox with a new level of tools? Statistics II For Dummies, 2nd Edition, picks up right where Statistics For Dummies, 2nd Edition, (John Wiley & Sons) leaves off and keeps you moving along the road of statistical ideas and techniques in a positive, step-by-step way.

The focus of Statistics II For Dummies, 2nd Edition, is on finding more ways of analyzing data. I provide step-by-step instructions for using techniques such as multiple regression, nonlinear regression, one-way and two-way analysis of variance (ANOVA), and Chi-square tests, and I give you some practice with big data sets, which are all the rage right now. Using these new techniques, you estimate, investigate, correlate, and congregate even more variables based on the information at hand, and you see how to put the tools together to create a great story about your data (nonfiction, I hope!).

About This Book

This book is designed for those who have completed the basic concepts of statistics through confidence intervals and hypothesis testing (found in Statistics For Dummies, 2nd Edition) and are ready to plow ahead to get through the final part of Stats I, or to tackle Stats II. However, I do pepper in some brief overviews of Stats I as needed, just to remind you of what was covered and to make sure you’re up to speed. For each new technique, you get an overview of when and why it’s used, how to know when you need it, step-by-step directions on how to apply it, and tips and tricks from a seasoned data analyst (yours truly). Because it’s very important to be able to know which method to use when, I emphasize what makes each technique distinct and what the results tell you. You will also see many applications of the techniques used in real life.

I also include interpretation of computer output for data analysis purposes. I show you how to use the software to get the results, but I focus more on how to interpret the results found in the output, because you’re more likely to be interpreting this kind of information than doing the programming specifically. Because the equations and calculations can get too involved if you are solving them by hand, you often use a computer to get your results. I include instructions for using Minitab to conduct many of the calculations in this book. Most statistics teachers who cover these topics use this approach as well. (What a relief!)

This book is different from the other Stats II books in many ways. Notably, this book features the following:

• Full explanations of Stats II concepts. Many statistics textbooks squeeze all the Stats II topics at the very end of their Stats I coverage; as a result, these topics tend to get condensed and presented as if they’re optional. But no worries; I take the time to clearly and fully explain all the information you need to survive and thrive.
• Dissection of computer output. Throughout the book, I present many examples that use statistical software to analyze the data. In each case, I present the computer output and explain how I got it and what it means.
• An extensive number of examples. I include plenty of examples to cover the many different types of problems you’ll face. Some examples are short, and some are quite extensive and include multiple variables.
• Lots of tips, strategies, and warnings. I share with you some trade secrets, based on my experience teaching and supporting students and grading their papers.
• Understandable language. I try to keep things conversational to help you understand, remember, and put into practice statistical definitions, techniques, and processes.
• Clear and concise, step-by-step procedures. In most chapters, you can find steps that intuitively explain how to work through Stats II problems — and remember how to do it on your own later on.

Throughout this book, I’ve used several conventions that I want you to be aware of:

• I indicate multiplication by using a times sign, indicated by a lowered asterisk *.
• I indicate the null and alternative hypotheses as Ho (for the null hypothesis) and Ha (for the alternative hypothesis).
• The statistical software package I use and display throughout the book is Minitab 18, but I simply refer to it as Minitab.
• Whenever I introduce a new term, I italicize it.
• Keywords and numbered steps appear in boldface.

At times I get into some of the more technical details of formulas and procedures for those individuals who may need to know about them — or just really want to get the full story. These minutiae are marked with a Technical Stuff icon. I also include sidebars along with the essential text, usually in the form of a real-life statistics example or some bonus information you may find interesting. You can feel free to skip those icons and sidebars because you won’t miss any of the main information you need (but by reading them, you may just be able to impress your stats professor with your above-and-beyond knowledge of Stats II!).

Foolish Assumptions

Because this book deals with Stats II, I assume you have one previous course in introductory statistics under your belt (or at least have read Statistics For Dummies, 2nd Edition), with topics taking you up through the Central Limit Theorem and perhaps an introduction to confidence intervals and hypothesis tests (although I review these concepts briefly in Chapter 4). Prior experience with simple linear regression isn’t necessary. Only college algebra is needed for the math details. Some experience using statistical software is also a plus, but not required.

As a student, you may be covering these topics in one of two ways: either at the tail end of your Stats I course (perhaps in a hurried way, but in some way nonetheless); or through a two-course sequence in statistics in which the topics in this book are the focus of the second course. If so, this book provides you the information you need to do well in those courses.

You may simply be interested in Stats II from an everyday point of view, or perhaps you want to add to your understanding of studies and statistical results presented in the media. If this sounds like you, you can find plenty of real-world examples and applications of these statistical techniques in action, as well as cautions for interpreting them.

Icons Used in This Book

I use icons in this book to draw your attention to certain text features that occur on a regular basis. Think of the icons as road signs that you encounter on a trip. Some signs tell you about shortcuts, and others offer more information that you may need; some signs alert you to possible warnings, while others leave you with something to remember.

When you see this icon, it means I’m explaining how to carry out that particular data analysis using Minitab. I also explain the information you get in the computer output so you can interpret your results.

I use this icon to reinforce certain ideas that are critical for success in Stats II, such as things I think are important to review as you prepare for an exam.

When you see this icon, you can skip over the information if you don’t want to get into the nitty-gritty details. They exist mainly for people who have a special interest or obligation to know more about the technical aspects of certain statistical issues.

This icon points to helpful hints, ideas, or shortcuts that you can use to save time; it also includes alternative ways to think about a particular concept.

I use warning icons to help you stay away from common misconceptions and pitfalls you may face when dealing with ideas and techniques related to Stats II.

Beyond the Book

In addition to all the great content included in the book itself, you can find even more content online. Check out this book’s online Cheat Sheet on dummies.com. It covers the major formulas needed for Statistics II. You can access it by going to www.dummies.com and then typing “Statistics II For Dummies Cheat Sheet” into the search bar.

I’ve also included two major data sets that are analyzed in Chapters 20 and 21, so you can follow along with me or do your own analysis (not required!). Go to www.dummies.com/go/statisticsIIfd2e to access these files.

Where to Go from Here

This book is written in a nonlinear way, so you can start anywhere and still understand what’s happening. However, I can make some recommendations if you want some direction on where to start.

If you’re thoroughly familiar with the ideas of hypothesis testing and simple linear regression, start with Chapter 5 (multiple regression). Use Chapter 1 if you need a reference for the jargon that statisticians use in Stats II.

If you’ve covered all topics up through the various types of regression (simple, multiple, nonlinear, and logistic) or a subset of those as your professor deemed important, proceed to Chapter 10, the basics of analysis of variance...