Right, mature cards are cards with >=21 day interval. That’s honestly quite an arbitrary number. And young cards are cards with <21 day interval.
The analysis generated by FSRS optimizer is more accurate.
Are you referring to the new analysis table that you recently added to v3.2.0?
In your other thread, you mentioned
The average interval is coming from Anki SM2 and the delay that you actual reviews.
The average retention is coming from your reviews at those intervals.
if your retention is less than 90%, it means that the default interval is too long for you. If it is bigger than 90%, the interval is too short.
This is very interesting.
Here’s my friend’s pre-training analysis table:
r_history avg_interval avg_retention stability factor \
1 1 1.0 0.6486 0.2435 inf
2 3 1.0 0.9532 2.1974 inf
7 3,1 1.0 0.8732 0.7780 0.3541
8 3,2 2.4 0.8828 2.1599 0.9829
9 3,3 3.0 0.9513 6.3821 2.9044
30 3,3,1 1.0 0.9407 1.7330 0.2715
32 3,3,3 6.9 0.9539 15.4016 2.4132
81 3,3,3,1 1.0 0.9533 2.2030 0.1430
83 3,3,3,3 16.8 0.9501 35.8667 2.3288
161 3,3,3,3,1 1.0 0.9512 2.1091 0.0588
163 3,3,3,3,3 41.8 0.9430 77.7765 2.1685
256 3,3,3,3,3,1 1.0 0.9617 2.6979 0.0347
258 3,3,3,3,3,3 104.2 0.9344 166.4570 2.1402
349 3,3,3,3,3,3,1 1.0 0.9570 2.4300 0.0146
350 3,3,3,3,3,3,3 226.5 0.9055 242.0319 1.4540
455 3,3,3,3,3,3,3,1 1.0 0.9328 1.5146 0.0063
group_cnt
1 6891
2 8218
7 395
8 171
9 7583
30 372
32 6978
81 300
83 6379
161 317
163 5771
256 313
258 3977
349 278
350 1191
455 119
In particular, we can see that pressing Good 6 times for a hypothetical card:
r_history avg_interval avg_retention stability factor \
...
258 3,3,3,3,3,3 104.2 0.9344 166.4570 2.1402
...
If I understand this table correctly, Anki SM-2 will give him an average interval of 104.2 days, whereas FSRS will suggest an stability of 166.4570 (approximately 166.4570 days that is predicted to give us a 90% retention rate). So there’s a huge increase here for him.
Contrastly, my table:
r_history avg_interval avg_retention stability factor \
1 1 1.0 0.9223 1.3058 inf
2 3 1.0 0.9230 1.3918 inf
6 3,1 1.1 0.9539 2.5066 1.8010
7 3,2 2.7 0.8365 1.5963 1.1469
8 3,3 2.8 0.9474 6.1363 4.4089
19 3,3,1 1.1 0.9752 4.6229 0.7534
20 3,3,2 3.7 0.9639 9.4033 1.5324
21 3,3,3 6.0 0.9778 26.3843 4.2997
52 3,3,3,2 6.5 0.9555 15.0628 0.5709
53 3,3,3,3 12.9 0.9643 34.9486 1.3246
104 3,3,3,3,1 1.0 0.9744 4.0627 0.1162
105 3,3,3,3,2 16.9 0.8746 11.7997 0.3376
106 3,3,3,3,3 29.3 0.9398 46.1356 1.3201
174 3,3,3,3,3,1 1.1 0.9779 4.8879 0.1059
175 3,3,3,3,3,2 41.5 0.8120 18.0562 0.3914
176 3,3,3,3,3,3 51.0 0.9252 65.0278 1.4095
275 3,3,3,3,3,3,3 36.7 0.9645 97.8701 1.5051
394 3,3,3,3,3,3,3,3 86.1 0.8260 48.1421 0.4919
group_cnt
1 16340
2 7852
6 722
7 706
8 6235
19 253
20 721
21 4772
52 277
53 3615
104 117
105 148
106 2363
174 131
175 139
176 1229
275 579
394 107
In particular, pressing Good 6 times for a hypothetical card
r_history avg_interval avg_retention stability factor \
...
176 3,3,3,3,3,3 51.0 0.9252 65.0278 1.4095
...
Anki SM-2 will give me an average interval of 51 days for the card, and FSRS will give me a stability of 65.0278 (65.0278 days that is predicted to give us a 90% retention rate).
Interestingly enough, my friend’s data shows that Anki SM-2 intervals is too short for him, and he can have larger intervals using FSRS, since his average retention is above 90%.
On the other hand, my data shows that Anki SM-2 intervals are too large, there are instances where my average retention drops below 90%; particularly
r_history avg_interval avg_retention stability factor \
...
394 3,3,3,3,3,3,3,3 86.1 0.8260 48.1421 0.4919
This massive drop in retention to 82.60% is quite huge, and I definitely feel like I’m doing more reviews using Anki SM-2 because of that. If my retention was 90%, I wouldn’t be doing as many reviews. FSRS may suggest shorter intervals than SM-2 for me, but I feel like there’s that optimal spot between the interval spacing and retention rate where you do the least amount of reviews. In other words, Anki SM-2’s algorithm, although it gives you large intervals, it could give you more reviews if you’re not actually hitting that 90% retention rate. Conversely, with FSRS, it could give you shorter intervals, but if that means being able to increase your retention rate to 90%, then you potentially might be doing less cards, since you’re not failing so many cards and having to relearn them.
There’s also some things to consider between my friend and me though with how we review our cards. I tend to fail fast, I have an average of 3-4 seconds review time per card. Whereas my friend has an average of 6-9 seconds per card, taking a bit more time to review the cards, which potentially may affect our retention rates, due to how we review our cards differently.