A key operational difference is that the design challenge requires that criteria for success be defined while the scientific method does not. While both are similar, the differences are still real and we need to practice both processes.
With these key differences between the two process, we can see one is used to eliminate answers, while one is used to create them. When is it the right time to use each? how does one differentiate between the two in choosing which one is needed in a given situation? What situation calls for a design challenge process and what calls for a scientific method? When I think of scientific method, I think of a simple experiment with independent and dependent variables etc. in order to find the correlation between two things in a real life situation. While for the design challenge, I think of creating some kind of device or other solution to solve a real world problem. What other situations can be used for each and how does one decide?