What does Godhart’s law mean?

Question

It goes “When a measure becomes a target, it ceases to be a good measure.” How does that work in practice?

In: Other

Answer 1

Imagine that you want someone to learn how to do math. To see if they are learning, you give them a test. The test decides if they can go to the next grade, so it is super important.

Now, I could teach someone math OR I could teach them how to take this math test. That second situation is what we’re talking about here. My test no longer checks if you learned math, it checks if you learned how to take the test.

The most familiar outcome of this is when people talk about “teaching to the test”