Q: To what extent do you think these results show that the practice helped the students with their learning, versus it being the more diligent hardworking students who might have chosen to interact with your stack questions?
A: The average score decreased in both groups, but in the group that used STACK simulator, it decreased less than in the group that did not use this resource.
Q: So it was not a decision of the Students to take part in the stack exercise?
A: That's right. The decision was made by the teachers: which group will work with STACK simulator, and which without it.
Q: Were both Groups of comparable strength initially?
A: The groups were comparable, and at the initial testing (at the beginning of the first semester), their average scores differed slightly (the hypothesis about the significance of the discrepancy between the sample averages was tested).