Last year while working on some public opinion polling software I ran into an issue where I found that analysts often wanted to know the difference between some

Last year while working on some public opinion polling software I ran into an issue where I found that analysts often wanted to know the difference between someone selecting "None", someone skipping the question, or someone not being asked the question due to branch logic. It's a pretty easy problem to solve -- if you represent the response as a string, you use "None", "", and "Not Asked"; if you represent as numeric, you just set numeric codes for each. But the interesting thing is just that it's sort of an invisible distinction until you think about it, just like this one is. I don't really do a lot of UX stuff myself and it was kind of a cool moment to have to think about it a little.