You may have noticed in YES that there's no textbook required for this course. That's not entirely accurate, but it is true that you don't need to buy a textbook. Your readings will come from OpenIntro Statistics, an online, free, open statistics textbook. Let's take those adjectives one at a time:
- Online - OpenIntro Statistics is available as a PDF. You can download the entire book as a single file or download individual chapters.
- Free - Those PDFs are free of charge. If you'd like a hardcopy without printing it yourself, you can purchase a print version of the book on Amazon for $9.02.
- Open - The PDF version of the book has a Creative Commons BY-NC-ND license, which means you can make as many copies of it as you like as long as (BY) you attribute the authors, (NC) you don't use your copies for commercial gain, and (ND) you keep the PDFs as they are (no derivative works). The source code that generated those PDFs (that is, the text of the book itself) is even more open. It has a Creative Commons BY-NC-SA license, which means you can make derivative works (like your own remix of the textbook) as long as you (SA) "share alike," giving your derivative works the same Creative Commons license.
So there is a textbook required for this course, but (a) the online version is free and (b) the print version is cheap.