Qualification problem

Imagine you have a big jar full of balls. Some balls in the jar are blue, some are red, some are green, and some are yellow. Now, you want to create a rule that tells you which balls are green. So, you think of a rule that says, "all balls that are green will have the letter 'G' written on them."

But, suddenly, someone gives you a new green ball that doesn't have the letter 'G' on it. Now, your rule doesn't work anymore! This is called a qualification problem. It happens when a rule or theory is made, but then there are exceptions to that rule that weren't accounted for.

In real life, qualification problems happen a lot when scientists are trying to create rules or theories about complex systems, like the environment, the economy or human behavior. They might make a rule, but then something unexpected happens, and the rule doesn't apply anymore.

Scientists and researchers have to keep adjusting their rules and theories as they learn more and more about a complex system, to try and avoid qualification problems.