Or is it?
Humans are not very good at generating random sequences; when asked to come up with a “random” sequence of coin flips from their heads, they inevitably include too few long strings of the same outcome. In other words, they think that randomness looks a lot more uniform and structureless than it really does. The flip side is that, when things really are random, they see patterns that aren’t really there.
I can try now, even though it’s not working? Gee, thanks.
Come visit any time we aren’t at home.
When I taught I tried to instill the concept that you should be able to pass an exam without a single correct numerical answer, because the problem set-up was the most important part of the solution. Few of my students believed me, but I see that my experience was not unique. The First Excited State has Missing the Important Stuff, which sets up a response at Uncertain Principles, The Process Is as Important as the Answer
Chad points to the problem of giving a problem with only algebraic expressions
The problem with this method, of course, is that students hate it with the burning passion of a million white-hot suns. If you think they get unhappy when they don’t have the exact numerical answers to work toward, just wait until you see their reaction to no numbers at all.