I mean it doesn't really matter because you just end up balancing one against the other but the wikipedia form of the drake equation and the slides form both us

I mean it doesn't really matter because you just end up balancing one against the other but the wikipedia form of the drake equation and the slides form both use fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations) fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space