Measuring improvement in 3D tasks I have been teaching 3D design for a while, and i have noticed that a small group has decidedly hard time coping with rotation of the virtual camera. Unfortunately designing in 3D on a screen requires you to do quite a lot of mental rotation.
Instead would like to setup a test to see if a VR setup would alleviate the problem on a individual level.

Now i am aware of this near duplicate, that says men score better. But its not entirely fair in this case, as many of the problem cases are male. In either case i am looking for what improvement can get done on a personal level by optimizing the tools to the user, notwithstanding the general trend of the masses.

How do begin to designing the test for measurement of improvement?
How do [I] design [a] test for measurement of [3D rotation] improvement?


The way to start is to define what you wish to measure. 


What needs to be mentally rotated? 
Why does it need mental rotation? 
What goal needs to be reached by the task?
Are the tasks a matter of correct or incorrect, or is it a graded measure?


Only then can you start thinking about the question proper, namely how performance can be measured.