9 times out of 10
"One anonymous coward considered this and brought up one of the best-known rules of science, at any rate the science one learns - as we learn ours here at the Reg - mostly from chaps in the pub.
But what about if by a million/billion/whatever to one chance we are the first "intelligent life" to emerge. Someone has to be, and we all know that the thing about million to one chances is that they happen nine times out of ten."
Or indeed the Discworld books.
Ready. "It's a million to one chance..."