About minimum recommended retention (CMRR)

hi everyone,

on one of my own topics here, someone said that as a general rule, the higher your true retention rate is, the higher the CMRR. this is something that I absolutely don’t understand. it goes exactly against my own reasoning.

a high true retention rate means the deck is easy for you to memorize. so I was assuming that you needed to review each card less often (because they’re so easy to memorize), and less often means a lower desired retention rate, right ? so the idea is that when a deck is easy, there’s no need to spend too much time on it.

on the contrary, when the deck is hard, the CMRR diminishes. but if a deck is hard, you should work harder to memorize it. if the review interval is too big, you won’t remember anything at all. basically, the harder a task is, the more energy you need to spend to do it. apparently, CMRR says the opposite : it’s too difficult, relax, space out your repetitions and it will magically work better ?

I’m completely lost, thank you in advance for shedding light.

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Since you’re responding to something in one of your other posts, I’m going to merge these together.

I think you’re confusing “retention” and “desired retention”.

The true retention depends on:

  1. How well FSRS performs for your deck which will partly depend on how homogeneous the cards are aka how similar they are.
  2. The desired retention you set.

If you have high overall retention for a preset, it means you’ve set high desired retention and not that the cards are easy.

it’s too difficult, relax, space out your repetitions and it will magically work better ?

CMRR is trying to come up with a desired retention that maximises knowledge:workload.

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that raises a question : does FSRS understand that when reviewing cards, both directions are extremely different ? one is a lot easier than the other.

well, your ultimate desired retention is always 100%, right ? we all start at 90% because before FSRS, Anki was saying that 90% was most efficient in terms of knowledge/workload. but really, what I want is to remember absolutely every card.

not really, I started with 90% desired retention because of what I said above. and my true retention rate started to improve and CMRR told me set the desired retention higher up. and then again, and again.

on the deck I’m struggling more with, CMRR is much lower.

Nope, @expertium says it’s not important. I previously suggested to calculate the times by dividing the data for cards into different quartiles.

No, FSRS makes sure it’s always 90 percent. It’s not like you’ll set it to 90 percent and it’ll become 100 percent on its own. Though, in the long-term, it just might.

I think that’s just an optimisation problem and happens with me too. If you keep the params optimised, and after having sufficient reviews it wouldn’t suddenly start to increase to 100 percent.

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