In SM-2, how do you rate a review, and what counts as a failure?

You grade recall quality $q$ on a 0–5 scale: $q=5$ is perfect, $q=3$ is correct but hard, and anything $q<3$ is a lapse (failure).

The grade drives everything downstream:

• $q \ge 3$ → a pass: the interval grows and the ease factor is nudged.
• $q < 3$ → a lapse: the card is treated as forgotten.

A single number carries both "did you get it?" and "how easily?", which is SM-2's strength (simplicity) and its weakness (it only ever sees your self-report, never the true odds you'd recall the card).