I don’t know if you are familiar with this term. If you aren’t, I wish you would read the above wikipedia link and think about the implications.
Chances are that it will delightfully assist you in categorizing a few people in your life. We all know someone whose bulb is somewhat dim but doesn’t see themselves as less-than-capable.
Once you understand the Dunning-Kruger Effect, you will be able to see people in a new light, albeit one that might not be the most flattering to them.