Permanent link to Stat of the Week: Log-5"Log-5" is a method introduced by Bill James to predict the probability of victory when two teams of a given winning percentage play against each other. The formula is:

WPct = A - ( A x B ) / (A + B) - ( 2 x A x B )

Where "A" is Team A's winning percentage, and "B" is Team B's winning percentage. In the simplest terms, this formula indicates how often Team A should beat Team B.

Imagine that Team A wins 50% of its games and Team B wins 38% of its games. Inputting these percentages (as a decimal) into the formula above would yield:

WPct = 0.31/ (0.88) - (0.38) =

0.62Or, in other words, Team A should beat Team B 62% of the time.

Permanent link to Stat of the Week: LeverageLeverage measures how important a given situation is during a game (relative to the start of the game). The start of a game is defined as a Leverage of 1.0, a neutral situation. As the game progresses, the Leverage can fluctuate based on the inning, the number of outs, the runners on base, and the difference between the two teams' runs scored so far.

Leverage is the ratio between how much a single run scored changes the expected probability of winning in the current situation and how much a run would have changed the expected probability of winning at the very beginning of the game.

For example, if a run scored in the eighth inning increases the probability of winning by 20%, while a run at the start of the game increases it by 10%, then the Leverage of the situation in the eighth inning is 20%/10% = 2.00 Leverage.

Permanent link to Stat of the Week: APRAPR, or Adjusted Pitching Runs, measures the number of runs a pitcher prevented as compared to a league-average pitcher in a neutral park in the same number of innings. Derived from the pitching component of linear weights, or pitching runs, APR includes an adjustment for ballparks and is based on all runs allowed, not just the earned runs.

APR = L x IP - (R/PF)

Where "L" is the league average of runs per inning and "PF" is the park factor for the pitcher's home park.

Permanent link to Stat of the Week: RARA, or Run Average, is the number of runs (earned and unearned) allowed by a pitcher or team per 9 innings. Considering

allruns allowed by a pitcher is more desirable from a predictive standpoint because it adjusts the arbitrary format of official scoring and the attribution, the problems of reconstructing an inning to determine unearned runs, and the small number of errors presently compared to the past that would normally be seen when measuring pitcher success through just an "earned runs" method. A pitcher good at preventing earned runs tends to be good at preventing unearned runs.

Permanent link to Stat of the Week: Pythagorean RecordCredited to the Greek mathematician Pythagoras for describing the sides of a right triangle. Around the year 1980, Bill James, American baseball writer and statistician, discovered that you can tell how many games a team

willwin, based on its runs scored and runs allowed using a formula containing "three squares" like the pythagorean formula.

Pythagorean Record:

Winning % = (runs scored)^2 / [(runs scored)^2 + (runs allowed)^2]The winning percentage is, of course, approximate and can be more accurate by adjusting the exponent. This adjustment is known as "Pythagenport", named after Clay Davenport who used logarithmic formulas to estimate the adjustment exponent based on runs scored and allowed. Later revisions to this method have been made.

Permanent link to Stat of the Week: Playoff Success Points (PSP)PSP is a measure designed by Nate Silver to indicate a team's success in the postseason in divisional play. PSP assigns points to playoff teams as follows:

- 3 points for making the playoffs
- 3 points for winning the League Division Series (LDS)
- 4 points for winning the League Championship Series (LCS)
- 4 points for winning the World Series
- 1 point for each postseason win
- -1 point for each postseason loss
The highest possible PSP is 25, for a team that sweeps through all eleven postseason games, while the lowest is 0, for a team that is swept in the first round.