Memory

How Yumio Memory works

Memory keeps a score for every topic you practise. The score is a guess about how likely you are to get a fresh question on that topic right today. It goes down when time passes and up when you practise.

What the strength number means

If a topic says 70%, Yumio thinks you would get about 7 in 10 new questions on it right if you sat them now. It is an estimate from your own answers, not a promise about your exam marks.

Why it drops over time

Everyone forgets. For each topic Yumio keeps a number called stability: roughly how many days until you would only recall the topic 9 times out of 10. The longer it has been since you last practised, the lower your chance of recalling it, so the strength falls a little each day. A topic you have not touched for a month shows lower than the same topic yesterday.

What moves it up

• A right answer after a real gap helps more than a right answer straight after the last one, and a hard question helps more than an easy one.
• A right answer after a real gap makes the topic last longer before it fades, so it comes back less often.
• Answers you give within 6 hours of each other count as one sitting, so a streak of ten quick answers is not ten separate proofs.

What moves it down

• A wrong answer makes the topic fade sooner. A first slip on a topic you know well counts for less. Wrong answers on several different days in the last six weeks count for more.
• If your last sitting on a topic went badly, the strength is held down by it, even if your older record was good.
• Old results fade out of the picture, so a topic you were good at months ago does not stay strong on its own.

When a topic comes back

Yumio asks you about a topic again just before it is likely to fade, so each review is as useful as it can be. The more securely you know something, the longer the gap, but it is never left for ever: a known topic still comes back for a refresher at least every 60 days, or 120 days after a long strong record.

Mistakes and the reason for each one

Every wrong answer is saved in Mistakes. Where your answer shows a reason, Yumio names it: left blank, a sign slip, the same wrong answer again, or several different questions wrong on one topic. When your answer does not show a reason, Yumio says nothing rather than guess.

Streaks and freezes

Practising on a day keeps your streak going. You earn a streak freeze for every 7 days of revising, and you can hold up to 2. A freeze covers one missed day so the streak does not reset. Freezes are never bought.