Hi everyone,

Later this year I will be conducting a repeated measures longitudinal experiment designed to quantify the long-term impact of Mixed Reality displays as user interfaces for viewing flight procedures/checlists on drone piloting performance.

Prior to testing, participants will receive training from instructors, and over the course of this training period, will execute 2 different drone flights (as shown in the image attached as 'Position Flight' and Traverse Flight').

Participants will be randomly assigned into 1 of 2 groups - the 'Hololens First' group, or the 'Screen First' group (an LCD screen is the control display condition). I will also be ensuring that an equal number of participants are assigned to each group.

Following the completion of the training flights, participants will perform three subsequent test flights:

• Test Session 1 will involve participants executing 2 different flights not seen in training (shown in the image attached as 'Orbit Flight' and 'Recon Flight'), and will take place roughly 5 minutes after the completion of training.
• Test Session 2 involves participants returning 10 days after Test Session 1 to conduct the same flights they executed in Test Session 1 (Orbit Flight and Recon Flight).
• Test Session 3 involves participants returning 180 days after Test Session 1 to conduct the same flights they executed in Test Session 1 (Orbit Flight and Recon Flight).

My question, therefore, is do I need to randomise my participants into the Hololens First group or the Screen First group prior to each test (i.e. randomise participants before Test Session 1, randomise them again before Test Session 2, and finally, randomise before Test Session 3), or if it is okay to randomly assign participants to one of these groups prior to their training flights commence - with participants remaining in either the Hololens First Group or the Screen First Group for the entire duration of the experiment?

Thanks a lot in advance for your help - it is much appreciated!

Cian