If you pray for rain, and it just happens to rain then you could 'look at the odds.' And it might be there was a ten percent chance
of rain. So you can't tell. And besides, what interest does God have in your rain gauge, given that that whole bible is about the
way to go to heaven, and worrying about earlhly matters?
But if you pray for God's wisdom, guidance, grace, forgiveness etc and you (and everyone else) sees a change come into your
life, things happening that you had no power over, then you might want to consider God has answered an honest and wholly
appropriate prayer.
On the contrary, once again there was a chance of things happening that way. Possibly a good chance. So once again, there is no conclusion possible either way.
The difficulty is that all positive evidence for God seems to be very similar to confirmation bias and all evidence against God is said to not satisfy the faith requirements, and so is a 'no true Scotsman' issue.