The number of solutions developed by students during the teaching unit was assessed two
times during the teaching unit using a 4-point scale. After the first session, students were
asked about the number of solutions they developed for the first and second problems
and after the second session about the number of solutions they developed for the third
and fourth problems. One sample item was While solving the ‘Fire-brigade’ problem, I
developed (0=no solution; 1=one solution; 2=two solutions, 3=more than two solutions)
today. In order to simplify the interpretation of this scale, the last two categories were
aggregated into the category two and more solutions.1 Thus, this scale ranged from 0
(no solutions) to 2 (two and more solutions)