Experiment #1:
Every day for 30 consecutive days offer 3 different prayers -
Prayer 1 - Ask Jehovah for X
Prayer 2 - Ask Thor for Y
Prayer 3 - Ask Zeus for Z
At the end of 30 days tally which god granted the most prayers.
If Jehovah grants 0 prayers and the gods grant any prayers a JW might say that it was Satan who was granting those prayers and that Jehovah didn't grant any of prayers because you were praying to false gods. However, how would Satan be able to grant any prayer in less he too is a listener prayers - omniscient?
Experiment #2
For 30 consecutive days offer a prayer asking for the same thing to Jehovah, Thor, and Zeus.
At the end of 30 days tally the number of prayers granted.
If any prayers were granted this would once again be refuted by JWs as Satan at work. However, once again, that would mean that Satan is a mind reader, omniscient, a hearer of prayers.
Experiment #3
Prayer to Jehovah for reasonable things such as "Please help me obtain a new job. Please help me pay the rent. Please help me find new clothes for the meetings." Then, only do spiritual activities - go to meetings, participate in the ministry, do Bible study. Do this for 30 consecutive days. Do not do anything on your own to further your requests (e.g. apply for jobs). After 30 days, stop praying for those things and only act on your own to obtain them.
At the end of 60 days see which method helped obtain your goals.