Match Statistics
How BackgammonDB measures a match — the equity-loss error bands and their colors, what counts as good vs. best, dice luck, and a link down to Performance Rating.
BackgammonDB sums a match up two ways: how well you played (the error bands, and the Performance Rating built from them) and how the dice treated you (luck). You read these on the match & game stat sheets and the progression graphs during review; this page explains what the numbers mean.
The atom underneath all of it is equity change: the estimated chance of winning the match before the roll, after your roll, and after you played a move.
A lucky move is one where your match equity increased from before the roll to after the roll. Luck assumes you then play the best move. Skill is based on how much equity was lost between the best move and the one you played.
Error bands
Every analyzed decision's equity loss is sorted into a named band. The bands drive the colored error dots in the action list, the candidate deltas, the error counts on the stat sheets, and the severity filters everywhere.
| Band | Equity loss |
|---|---|
| Good | better than the error threshold |
| Doubtful | error → ⅓ of the way to blunder |
| Bad | ⅓ → ⅔ of the way to blunder |
| Very bad | ⅔ of the way → the blunder threshold |
| Blunder | blunder threshold → howler threshold |
| Howler | beyond the howler threshold |
Changing the thresholds
Three thresholds can be set directly. When you do this, every position, match and view will update to reflect your new error bands.
- Error threshold (default −0.020, the XG-standard line) — where good ends.
- Blunder threshold (default −0.080) — where blunder begins. The three bands between error and blunder (doubtful, bad, very bad) just divide that gap evenly, so moving either end re-spaces them automatically.
- Howler threshold (default −0.250) — a howler is a blunder bad enough to clear this line. It's BackgammonDB's own most-severe band, sitting beyond XG's blunder boundary, so you can single out the real disasters.
All three live in settings. The Alt+Arrow error-jump uses a separate navigation threshold, so you can hop only between severe mistakes without recoloring the list.
Good vs. best
Two ideas sound alike but aren't:
- Best is the literal top candidate — rank 1 in the candidate list.
- Good is a band — your move's equity loss was within the error threshold, so there's nothing to flag. A good move need not be the top move; it just wasn't considered a mistake.
By default, good moves are not flagged as errors and they aren't highlighted with dots. On the board the engine's best move is drawn as its own green dotted overlay arrow, so you can always compare it to what you played.
Two settings tune this:
- Good-move indicators add a green dot to correctly-played (good) moves, not just to mistakes.
- Hide best overlay when correct suppresses the best-move arrow whenever your played move was good (within the error threshold) — not only when it was literally the best. So a good-enough move leaves a single clean arrow, and the overlay reappears only when you actually erred.
Luck
Alongside skill, BackgammonDB reports dice luck — how much equity each roll gained or lost purely from the dice, taken straight from the analyzed file. Only rolls carry luck; cube and take decisions don't.
Luck is zero-sum and mirrored: a roll that helps you by x hurts your opponent by x, so the two sides' figures are exact opposites. Two numbers are reported:
- Luck equity — the total signed equity the dice handed you over the whole match (your roll-luck minus your opponent's).
- Luck per roll — that total spread over the number of rolls, which is the headline figure and what maps to the descriptive band below.
| Luck per roll (equity) | Band |
|---|---|
| ≤ −0.040 | Not your day |
| −0.040 to −0.030 | Very unlucky |
| −0.030 to −0.020 | Unlucky |
| −0.020 to −0.010 | Quite unlucky |
| −0.010 to −0.002 | Average |
| −0.002 to +0.002 | Insignificant |
| +0.002 to +0.010 | Average |
| +0.010 to +0.020 | Quite lucky |
| +0.020 to +0.030 | Lucky |
| +0.030 to +0.040 | Very lucky |
| ≥ +0.040 | It's in the wrist |
A joker is a single roll whose luck swing clears a threshold in your favor (your own lucky roll, or your opponent's unlucky one); an anti-joker is one that clears it against you. Because luck is mirrored, your jokers are your opponent's anti-jokers. The joker threshold defaults to 0.300 and is adjustable in User Settings.
Luck and skill are independent: a great PR in a match you also got lucky in is still a great PR. The two are reported side by side so you can tell a good result from a fortunate one.
Performance Rating
Performance Rating (PR) is the single skill number built from your equity losses — lower is better, and it's computed exactly the way eXtreme Gammon does it so your figures line up with XG's.
→ See Performance Rating for the formula, which decisions count, the skill bands, and how PR pools across many matches.