SM-2

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Open source algorithm for spaced repetition developed by Piotr Wozniak from the late 1980s. Used in Anki.

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Subsequent versions of this algorithm are not open source, and used in Supermemo

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Algorithm Details

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EF = 2.5
I(1):=1
I(2):=6
for n>2: I(n):=I(n-1)*EF

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For each correct response between 0 and 5
EF’:=EF+(0.1-(5-q)*(0.08+(5-q)*0.02))
Minimum EF = 1.3

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References

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