*This article explains the design choices and math behind RemNote's exam scheduler. While you'll get a better experience from the exam scheduler if you fully understand it, if you're looking for practical advice on getting ready for an exam right now and you don't have the time to spend fully understanding it yet, check out Preparing for an Exam first*!

# The problem

Traditional spaced-repetition algorithms optimize for remembering the largest possible volume of information as efficiently as possible over an indefinite time period. They do a great job at this! But if you have exams coming up, that’s probably not quite what you want – instead, you want to optimize for remembering some set of material as well as possible at one short moment in time. (Of course, these goals aren’t mutually exclusive – you can keep practicing your material after your exam if you think it’s worth remembering long-term.)

RemNote is the first general-purpose spaced-repetition tool to offer automatic scheduling adjustments for students preparing for exams.

# Spaced repetition background

To understand how RemNote adjusts for exams, we need a quick refresher on how memory works. Spaced repetition requires considering at least two facts about your memory of each card which change over time:

A card’s

**retrievability**is the probability you’ll be able to successfully recall the answer within a short amount of time, if the card is presented to you for review. Retrievability decreases steadily over time, then jumps up to near 100% again when you recall the answer.

In spaced repetition practice, we aim to always keep the retrievability of our cards higher than some threshold (often called**desired retention**or**forgetting index**), so that we always have a good chance of remembering them when we need them. The amount of practice required increases exponentially as the desired retention approaches 100% – that is, each additional minute we spend practicing boosts our memory less than the minute before did – so most spaced repetition systems aim to maintain 85–90% retrievability, which is a good balance between usefulness and practice time. When a card's estimated retrievability drops below the desired retention threshold, it enters your queue for practice.

An important but poorly understood point is that your retrievability when recalling a random card at a random time – like when you need it in real life or on an exam – is*significantly higher than the desired retention*, as long as you stay more or less up to date on practicing your cards. That’s because the moment the scheduler puts a card in your practice queue is the moment you know it worst: your memory is now bad enough that you need a refresher, and once you get it, your memory will be much better again. A randomly selected card at a random time will, on average, be some time away from its next review, and thus have a higher retrievability. The math of actual moment-in-time retrievability is too complex for this article, but a good rule of thumb is that if your target retrievability is 90%, your actual retrievability on a random card at a random time is 95%.

A card’s

**stability**is how firmly the idea is stored in your memory. The higher a card’s stability, the slower its retrievability decreases over time. The more times you successfully recall a card, the higher its stability. Stability corresponds to a card’s*interval*parameter in a spaced repetition system, i.e., the number of days before the retrievability drops below some desired value.

On the forgetting curve, the *y*-axis shows the retrievability at any given date. The stability (and other factors like how difficult the card is and what other related cards you’ve practiced) determines how quickly the curve drops off.

# Changes made by the exam scheduler

First, understand that the “Exam Scheduler” is not a replacement for another spaced-repetition scheduler like Anki SM-2 or FSRS, but rather a complement to it. The main scheduler you have selected does most of the work, and the exam scheduler adds extra reviews or alters the parameters of the main scheduler as necessary.

Here are the changes it makes.

**Retrievability Period**(temporary increase in retrievability):*the day of your exam*is easy enough, if you’ve already achieved a solid understanding of those cards with a high stability. To make this happen, we add extra practice for all cards just before your exam.

**Maintenance Period**(temporary decrease in retrievability):*Consolidation Period*where the desired retention returns to normal, adding extra practice as needed.

(Why 70%? Reducing retention below 60–70% results in*increased*practice time, because the time spent relearning cards you’ve forgotten begins to exceed the time saved by practicing less often.)

**Extra Practice Sessions**: If you’re struggling to learn a card or you’ve recently forgotten it, and your exam is coming up in a day or two, you need to relearn it*now*, not at a “more efficient” time that comes after your exam. RemNote will compress the practice schedules of forgotten cards near your exam date so that you relearn them before the exam.

Ready to ace your next exam? Check out Preparing for an Exam to learn how to use the exam scheduler.