How do you know your design has solved the problem you set out to solve?
Wouldn't it be weird if you designed a solution and never stopped to ask "did I solve the problem"? This topic is concerned with gathering data to determine if you solved the problem you wanted to solve. Here's the important point: when you design a solution other people need to tell you if you solved the problem. You might think "sure! I did it", but actually, you need some data to support and prove you solved the actual problem.