Why are there different intervals used in paper SuperMemo, SuperMemo for Palm Pilot, SuperMemo for Pocket PC and SuperMemo for Windows?
Only SuperMemo for Windows computes accurate intervals that ensure achieving the desired forgetting index (assuming no overload and assuming the learning material is correctly formulated). For technical reasons, other SuperMemos use simplified algorithms (usually based on E-Factors, which lead to minimum computing). In addition, authors of individual SuperMemos often introduce their own modifications to the algorithm (e.g. limits on E-factor change, arbitrary first interval, interpretation of memory lapses, etc.). Paper SuperMemo is the least accurate. It uses fixed intervals for conglomerate pages of items. In such circumstances, it is not possible to differentiate between difficult and easy material.
