NCIDQ IDFX Sample Questions and Practice Exam Second Edition by David Kent Ballast. Published by PPI, A Kaplan Company. This is a study guide designed to help prepare for the Interior Design Fundamentals Exam (IDFX), part of the NCIDQ certification process. The book includes sample questions and a full practice exam to help you get familiar with the test format and content. It’s a solid resource for anyone studying for the IDFX or interior design certification. The material covers the fundamentals you need to know. Condition is used. Some normal wear from reading and studying, but the book is in reading condition and all pages are intact. No markings or writing inside.