This is an experiment which recreates the one I did as a Christian which convinced me to become an atheist. The simple experiment involved flipping a coin repeatedly both before and after praying for a certain result. Since that result is completely benign and harmless to everyone God should have no problem granting the prayer thus saving souls. If he really cares about our souls and wants us to believe, he will provide the result we've prayed for. If he does not we can say with evidence that prayer does precisely jack.