How do we know which transformation is occurring with blue/white screening?

[MrGenetic]

Books say 3 possibilities for this situation as insert within Lacz, insert outside Lacz, no inserted vectors, then these goes the transformation with Ecoli. But we can't know transformation yield %100. Thus, if we make blue white screening there is more possibilities.
Lacz-- inserted within white
Lacz-- inserted outside blue
Lacz-- no inserted blue
** No transformation white** ? ---> is this correct ? if it is correct, how we know the lacz inserted or not inserted clearly?

 

[Ygggdrasil]

Usually the plasmid contains an antibiotic resistance marker, so that cells which do not get transformed will die and not produce any colony.