The probability I was referring to is fl " in Drake's equation ("the fraction of planets that could support life that actually develop life at some point"), and Drake isn't really helping us here.
Quoting wikipedia:
The last four parameters, fl, fi, fc, and L, are not known and are very difficult to estimate, with values ranging over many orders of magnitude
Quoting wikipedia:
The last four parameters, fl, fi, fc, and L, are not known and are very difficult to estimate, with values ranging over many orders of magnitude