# Speed of learning vs. acquisition rate

**From:** Robyn
**Country:** Nov 28, 2000
**Sent:** {{{Sent}}}
**Subject:** Speed in statistics

**Question:**

I like your formula for knowledge acquisition rate. I made some estimations and was disappointed with my result (I learn philosophy and my items are a bit hard). Only some time later I discovered the parameter

Speedin statistics, and this displays even a lower speed value. IsSpeedand acquisition rate the same? Can you provide exact formulas?

**Answer:**

The overall formula is always the same:

AcquisitionRate = Memorized/(Days/365.25)/Workloadwhere:

Memorizedis the total number of memorized items,Daysis the number of days devoted to learning, andWorkloadis the average time spent for answering questions per day.

AcquisitionRateis always expressed in items per minute per year.However, the way

Workloadis determined may affect the ultimate result. Originally,Workloadwas supposed to stand fortime devoted to learning per day(in minutes). When theSpeedparameter was introduced, SuperMemo did not havetime per daystatistic. However, it hadBurden(items per day) andAvg time(average repetition time). This is why SuperMemo 9.5 (1999) usedWorkload=Burden*AverageTime. This formula survived until today.Also in 1999, SuperMemo introduced

Total time, which estimates total time devoted to answering questions. For older collections that value could only be estimated. This is whyTotal timecould not be used forSpeedestimations. Now, in 2016, most users have never used SuperMemo 9 (1998) or earlier. Moreover, in 17 years, total learning time would now be computed pretty accurately (estimated for the period 1987-1999 and computed exactly for the period 1999-2016).This is why, future SuperMemos will used

Workload=TotalRepetitionTime/Daysto accurately expressSpeed.All users who substantially overload their learning process will now see a boost to their learning speed parameter. This is not because of the better algorithm (Algorithm SM-17), but because

Speedbased onBurdenwould underestimate the speed of learning. The underestimate is caused by the fact that not all scheduled items are reviewed by the end of the day.To better account for material overload,

Speedwill also be multiplied byRetentionto truly reflect knowledge possessed (rather than auto-memorized in SuperMemo).To sum it up:

SuperMemo 9..16: AcquisitionRate = Memorized/(Days/365.25)/(Burden*AverageTime)SuperMemo 17..: AcquisitionRate = Memorized/(Days/365.25)/(TotalRepetitionTime/Days)*Retention