This article demonstrates how textbooks differ in their description of the term "experimental unit". Advanced Placement Statistics teachers and students are often limited in their statistical knowledge by the information presented in their classroom textbook. Definitions and descriptions differ among textbooks as well as among different editions of the same textbook. Furthermore, many schools use older editions of textbooks rather than current editions that contain updated information and thus lose the benefit of improved discussions and clarifications. Advanced Placement Statistics teachers should be aware of this issue and seek additional training through workshops, additional textbooks, and webinars to increase and strengthen their knowledge and understanding of key statistical concepts. Textbook authors should be aware of teachers' dependence on the authors' presentation of topics and ensure that key topics like "experimental unit" are covered thoroughly. This article considers three prior Advanced Placement Statistics exam questions to illustrate how different Advanced Placement Statistics textbooks may have influenced students' answers based on the textbooks' authors' treatment of "experimental unit". (Contains 3 tables.)