Is it useful / efficient to use an observer during Usability Testing?

I work in house at Twitter, so my perspective is different from one you'd get from a consultant. I have a research partner () but we often conduct research independently of each other, rather than taking notes for each other. I haven't talked to any researchers who can take notes while moderating; moderating is too mentally consuming to allow for anything else. However, we record our sessions using silverback and I watch the full videos after the sessions and take notes on the research I've moderated. This helps me become a better moderator because it forces me to watch my mistakes, and gives me thorough notes that I can build recommendations on. It also gives our team more flexibility. If my partner were to take notes during the session he would have to be free during those hours; he often has meetings during those times. Video files are reviewable at any point after the research. It's very important to have someone from the development team observing if possible, whether or not they are taking notes. That way they can give input on the research approach, add questions in, and vouch for your findings in meetings with the team after the research is done.

In my opinion, it's more cost-effective to include a Facilitator and a Recorder for every usability test.  If you try to be both a Facilitator and a Recorder, I feel that you either sacrifice quality or time. When I train my colleagues in-house, I purposefully define 4 primary roles: Participant (obvious), Facilitator, Recorder, and Observer.  I define these roles so people understand what their responsibilities are for a test. (Observer is not required to take notes but these folks are included in post-test KJ-Technique debriefing activity). Ideally, I prefer to have 3+ people available for any given usability test - the Participant, the Facilitator, and the Recorder. By including the Recorder, this frees up the Facilitator to perform his/her role to the fullest.  How can you engage the Participant and establish rapport if you are so focused on taking notes? How can the Facilitator see what's going on if s/he must divide attention between attending to the Participant, observing the test, and recording data? Because I involve an entire design team in our usability tests (designers, QA, engineers, etc.), I tend to prioritize as follows: * If I can have both a Facilitator and a Recorder, I tend to have the more "expert" researcher act as Recorder, because this person better knows what to look for and is trained to be more objective. * If I can only have one Facilitator, I make sure to record the test with software (such as Silverback, etc.).  Realistically, we do not always "go back to the tape" to watch recorded video, but this must happen if we do not include both roles.  If a Facilitator can be focused on the Participant and draw out good feedback, then this data can be retrieved later by watching the recording.  So, for every hour of testing, it requires 2 hours of "man-time" to account for Facilitator and Recorder roles.  Personally, I do not want to sacrifice data quality but sometimes I can sacrifice time. But I would vote including both roles so that resources are saved.

There's also the issue of training.  I always like to have an observer so that person can learn from me, and their feedback also helps me to learn.  It's also good to have someone there to make sure I don't forget anything important, which sometimes happens when we try to cram 9-12 hours of research into a single day to save on facility and hotel fees.   Since I do a lot of collaborative and multi-participant research, I need extra eyes and ears in the room to capture the details and alert me (as lead facilitator) to anything that needs to be probed, re-directed, addressed, etc.  I will also use an observer on a remote IM session to unobtrusively screen and present any questions or feedback from the out-of-room observers (whether in the next room or remote).   If there's a situation where I need to pinch every penny, I'll trade in the observer for a LiveScribe pen and fly solo, but I like having multiple people involved, and I think the observers are more receptive and responsive to the things they experience directly.

The observer can take notes and frees the facilitator from this task. The notes can make it easier later on to skip through large amounts of video/audio material.