"The Odds on Intelligent Life in the Universe"
The latest entry in the "Centauri Dreams" website:
Centauri Dreams – Imagining and Planning Interstellar Exploration (centauri-dreams.org)
discusses a Bayseian statistics analysis of the probability of intelligent life in the cosmos They point to this video for a more detailed exposition of the problem:
I can barely follow the math here, and I'm not sure I believe it, so you might want to check it out for yourself.