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Understanding Your Skill: The Glicko System in Pool

How we calculate your skill level and confidence in that number for league and tournament play.

1. Two Key Numbers: Rating and Confidence Score

The Glicko system tracks your pool skill using two numbers instead of one:

  • Rating ($r$): Your estimated pool skill score (e.g., a "B" player around 1500).
  • Confidence Score ($RD$): How certain the system is of your current skill level.

If your Confidence Score is **low** (meaning the system is very confident you are where you should be), your rating changes slowly. If your Confidence Score is **high** (meaning the system is uncertain of your true skill, like a new player), your rating can change dramatically after a single match.

2. Confidence ($RD$) Changes Over Time

The system dynamically adjusts its confidence in your pool skill:

3. Animation: The Confidence-Jump Relationship in Singles Pool

Click the buttons to see how the starting $RD$ (Confidence) changes the rating jump. The wider red zone is the potential change for a new player (High RD); the narrow green zone is for a veteran (Low RD).

1400
1600
START RATING (1500)
LOW RD (Veteran)
HIGH RD (New Player)

Player Rating: 1500

Example: Singles Pool Match Win

If two players—both with a 1500 Rating—win against the same average opponent:

  • New League Player (High RD): Wins $\approx$ 40 points. New Rating: 1540 (Quickly moving to an 'A' level).
  • Established Pro (Low RD): Wins $\approx$ 10 points. New Rating: 1510 (Rating stability is maintained).

The lower your Confidence Score (Low $RD$), the more stable your rating is.

4. Team Play: Simplified Steps for Rating Changes in Doubles

When you play a doubles match (or league team match), Glicko needs a fair way to distribute the result across the individual players. It does this in two simple stages:

Step 1: Calculate the Doubles Team's Overall Score

The system treats the two players as a single entity ("The Team").

Team Skill (The Average):

The team's overall skill is calculated based on the average of Player 1's and Player 2's ratings.

Team Confidence (The Certainty):

The team's collective confidence is calculated. Because you have two players, the team's combined skill is viewed as **more certain** than any single player's skill.

The team uses this combined score to determine how many points (the "prize" for winning) the team should win or lose against the opponent team.

Step 2: Share the Points Based on Individual Confidence

The points the team won or lost are now distributed among the players, but they aren't shared equally.

  • New/Inactive Players (High $RD$): They take a **bigger share** of the prize. The doubles match provides crucial new information, so they jump up or down much further.
  • Veteran Players (Low $RD$): They take a **smaller share** of the prize. The system is already very confident in their skill, so one doubles match barely moves their stable score.

**The Goal:** This system makes sure new players reach their true pool rating quickly, while protecting the stable, accurate ratings of veteran players from large swings caused by one team game.

Doubles Team Example: Splitting the Prize

Imagine a doubles team wins, earning a "prize" of 50 total Rating Points to distribute between its two players.

  • Player A (New Player, High RD): Receives $\approx$ **30-35 points** (The system uses the data to quickly refine their new rating).
  • Player B (Established Player, Low RD): Receives $\approx$ **15-20 points** (Their rating is stable and requires less adjustment from this single match).

The New Player's rating moves much more drastically than the Veteran's because the system is less certain of their true pool skill.