That raises the question “Why purchase the textbook?”
I’l give several reasons.
1. If you are taking a graduate course in your major, you should purchase all of the recommended texts. After all, you are planning to be a statistician and you’ll need a collection of books that will help you in your job.
2. There is a reason why authors write second editions of a book. In my case, I changed the LearnBayes package, and so I wanted to revise the book to be consistent with version 2.0 of the package. Also there are new sections and new exercises in the 2nd edition. The student is missing useful material. There was some confusion on the last homework, partly since the students were not reading the current edition.
3. “Books are expensive?” I understand a book can be expensive (actually, my text is relatively inexpensive), but it is certainly cheap relative to the cost of taking the course.
4. By not purchasing the textbook, the student is sending a message to the instructor, saying “I can get through the course without reading the book” which really is an insult to the instructor. This is common practice among undergraduates, but I hope it isn’t common among statistics students.