Variations in an exercise may be introduced under the following forms.<ol>

<li>Numerical variations

<li>Expressional variations

<li>Textual variations

<li>Graphical variations

<li>Mixed variations

</ol>

Variations are also divided according to their effects: those that affect the solution, and those that do not. Attention is usually focused on the former, but the latter is also useful, because they can teach students to pick up useful informations and discard useless ones.

It should be noted that the design of a high-quality multiple choice quizz with variations is often more difficult than that of a numerical problem. Ideally, all the possible choices should occur as good roughly with the same probability, a situation that is not always realisable.

Sorry but this chapter is still under construction.