One civilisation per galaxy... wonderful
Thinking like this that states "that suggests statistics of at least one civilisation per galaxy" always makes me laugh. Taking a single sample and attempting to extrapolate from it is utterly meaningless.
I think it was Douglas Adams that used exactly the same logic and stated that as space is infinite, and as there's a finite number of planets (one) known to have life, one over infinity equals nothing, so there isn't any life in the universe and any that you see is the result of a deranged imagination.
There's also a joke that I can't quite remember but I'll try my best.
Three statisticians were travelling to Scotland. As their train passed over the border, one exclaimed - "Oh look! A black sheep. All the sheep in Scotland are black!"
The second corrected him - "No, all it means is SOME of the sheep in Scotland are black."
The third thought for a while then announced - "You're both wrong. All it means is that at a minimum, there is one sheep in Scotland that is black on one side."