It's 100% and on Earth and everywhere.
What are the stats in the simple case, then?
Two planet model. 1st planet has life 100% probability. Second planet has life with unknown probability?
What is probability life exists in the two planet system?
100% Ok, but what is the probability it exists on places other than the first (certain, low entropy) planet? That's the question I think we're answering here, hahaha! :)