FDA CDRH’s “Do It By Design: An Introduction To Human Factors In Medical Devices ” December 1996. FDA has been increasingly concerned about human factors design a of medical devices to ensure safe and effective use of the devices by their intended users in their real environment. There many references to software design and user interfaces in this document as well as examples of human factor errors related to software. This document t also includes information and suggestions on how to design good user faces, pitfalls to avoid, and stresses the need for usability testing.