I am running a survey experiment and willing to relax “completely random” treatment assignment in order to have a roughly even distribution across my treatments with smaller n. 

"Evenly Present Elements" does this nicely, but I could not find a description of the actual algorithm running behind this option. Does anyone have the documentation somewhere?

This would be super important for understanding treatment assignment and to be able to convincingly claim causality---especially when random assignment was relaxed to conditional random. (And I don’t think “I ticked the box on qualtrics” explanation is sufficient in most cases.)