The presence of 2 prong outlets are a indicator of the general sufficiency of an electrical system. Residences built before 1965 were wired with 30- or 60-amp fuse panels. The 60-amp fuse panels had provision for at least one 240-volt wire for larger appliances, 30-amp fuse panels only provide 120-volt wiring. Both are totally inadequate for present day electrical needs.
These obsolete panels also had inadequate distribution of outlets throughout the structure.
Also it's most likely there won't be true grounding in the outlets that do have the three prongs. If a house has both 2 and 3 prong outlets, it's likely that the 3 prong outlets were just installed by a handyman for convenience. It's unlikely they're actually grounded.
Sometimes in the kitchen or bath they could have just grabbed the cold water pipe, but we have already seen that can be dangerous.
