but could understand how.
Example: part 1 - student chooses a frequency F for a sinusoid (1<= F <= 10).
I'll accept any answer as correct if it is in the interval [1,10].
part 2 - I draw a graph using the student's frequency F + dF, a random number and ask the student if this is the correct graph. If dF = 0, it is, if dF != 0 it is not.
this is not the complex problem that I'd use but it illustrates the concepts I'm after.