# The chords you miss come up more often

The random draw is weighted by your mistakes, and the chord stats page shows the ranking it uses.

## A weighted draw

If every chord in a pool comes up equally often, most of the time goes on the ones you already play without thinking, and the two you keep fumbling turn up no more often than C major.

So the draw is weighted. Every chord has a miss rate, and its weight rises steeply as the miss rate goes up. A chord you have just missed is more likely to come back within the minute, while the mistake is still fresh.

It is still a random draw: every chord in the pool keeps at least a tenth of its uniform chance, so none of them disappears and the session does not turn into the same two chords over and over.

## The two lists

[Chord stats](https://pianokitty.com/chord-stats) shows the ranking the draw uses: **To be perfected** on the left, **Perfected** on the right, both based on your last five practice sessions. These are not lifetime scores, so a bad week eventually drops out.

![The chord stats page: two columns of chord chips with miss rates and play counts, and a weakest-chords row below.](https://pianokitty.com/features/en/adaptive-practice/stats.webp)

![The "to be perfected" column: chord chips with a miss percentage and how many times each was played.](https://pianokitty.com/features/en/adaptive-practice/to-perfect.webp)

## Your weakest chord types

Figures for single chords jump around, but chord *types* give a steadier picture. The weakest-qualities row adds up the misses by type: half-diminished sevenths might be missed more than a third of the time, against 7% for plain minor triads. A figure like that is useful to bring to a lesson.

![A row of chord-quality chips, each with a miss percentage.](https://pianokitty.com/features/en/adaptive-practice/weakest.webp)

> The **Practice these chords** button at the top of the page opens the weak list in the [chord editor](https://pianokitty.com/editor) as a separate exercise.

## How the weighting works

- A chord is ranked only after you have played it a few times in the recent window, so one unlucky miss does not mark it as weak.
- Old counts fade as you keep playing the same chord, so improvement shows up instead of disappearing into a long-term average.
- A chord missed within the last minute gets an extra boost, so it comes back while your hands still remember the mistake.
- Every chord keeps a minimum share of the draw.

The weighting applies to the **chords** subject in random order, the only place with a pool to draw from. Scales, progressions and songs are played in their own order, so there is nothing to re-weight.

![The reinforcement-learning setting in Preferences, switched on, with a link to the chord stats.](https://pianokitty.com/features/en/adaptive-practice/setting.webp)

## Check your weak chords

- Try it: [See your ranking](https://pianokitty.com/chord-stats): The two lists, and your weakest chord types.
- Try it: [A harder pool](https://pianokitty.com/app?subject=chords&ct=6,7,8,10&bn=1,3,6,8,10&inv=0): Seventh chords and half-diminished, on black-key roots only.
- Try it: [Triads in every key](https://pianokitty.com/app?subject=chords&ct=0,1&bn=0,1,2,3,4,5,6,7,8,9,10,11&inv=0): Play a few rounds, then look at the stats page.
- Try it: [Drill a list by hand](https://pianokitty.com/editor): Type in the chords you know give you trouble.

Related: [Random chords + levels](https://pianokitty.com/features/random-chords.md), [The chord chart](https://pianokitty.com/features/chart.md), [The levels ladder](https://pianokitty.com/features/levels.md)

Source: https://pianokitty.com/features/adaptive-practice