Source: Wikipedia
Spaced repetition is an evidence-bases learning technique technique that is usually performed with flashcards.
Newly introduced and more difficult flashcards are shown more frequently, while older and less difficult flashcards are shown less frequently in order to exploit the psychological spacing effect.
Spaced repetition is commonly applied in contexts in which a learner must acquire many items and retain them indefinitely in memory. The use of spaced repetition has been proven to increase the rate of learning.
The idea behind spaced repetition derives from the concept of the forgetting curve, a concept that illustrates how information is lost over time when there is no attempt to retain it.
There are many implementations of spaced repetition, each using various algorithms. The most famous among these are Anki and SuperMemo 2.
The implementation in PSLE Science Coach is somewhat simplified version.
When you get a question correct, you do it the next day. Two times correct, do it again in two days. Same for the following times, but when you get a question wrong, you do it in 15 minutes. When you get that question correct, the days algorithm starts again.
U, A Question Q is pick randomlyQ is asked to the user
U response is correct:
S for this question Q and the user U is incremented by 1 :
S(Q,U) = S(Q,U) +1Q is hiden by 24hours times the number of success: now + S * 24hU response is wrong:
S for this question is reset to 0. S(Q,U) = 0Q is hidden for 15 minutes: now+ 15mn