Of course. And that would show up in the statistics. If most of the students in a class who studied with it are failing, rather than having a normal distributio

Of course. And that would show up in the statistics. If most of the students in a class who studied with it are failing, rather than having a normal distribution of grades, we know the book is not doing its job. The educator still gets useful information, and would know whether to continue using that textbook next term.