If you change two variables in an experiment, you can't tell which one yielded the results.
In Friday's case, there was also an added attraction for Hibs fans that Fenlon was in charge for the first time. Taken in combination with reduced (or free) cost of entry, and change of day, it's impossible to make any evaluation of the outcome.
If the SPL wants to conduct experiments, then fair enough, but they have to be controlled in a way that lets them make valid conclusions.
In the same way, my argument that reverting to every game kicking off on Sat at 3pm (or Wed at 7:45pm) and restricting live games will boost attendances, can never be validated without actually running a controlled experiment.