Which of the following is a principal task of the usability test moderator role?

The usability test moderator plays a crucial role during the execution phase of a usability test. Their principal task is to facilitate the test sessions by guiding participants through predefined testing tasks, observing behaviors, and ensuring that the test environment is neutral and free from bias. Defining testing tasks, however, is primarily done during the test design phase by the usability test designer or analyst, but the moderator ensures these tasks are clearly communicated and administered to participants during the session. Logging usability problems (option B) is often done by observers or analysts reviewing session recordings or notes, not directly by the moderator during live testing. Creating a survey plan (option C) and writing the usability test plan (option D) are preparatory activities generally done before the test sessions and are not the moderator's main focus. Therefore, the principal role of the moderator centers on conducting the sessions and managing task delivery effectively to obtain authentic user interaction with the system under test.