Series Win
How often one MLB team beats another over a series, and how long the series goes. Each team's expected win% comes from its runs scored and allowed per game; the two are combined head to head, with the higher seed getting home field.
How it works
Team xWin%: each team's Pythagorean win% with the PythagenPat exponent, from its regular-season runs scored (RS/G) and allowed (RA/G) per game: total_runs_factor = (RS/G + RA/G) ^ 0.285, then xWin% = RS/G ^ total_runs_factor / (RS/G ^ total_runs_factor + RA/G ^ total_runs_factor).
Head to Head: the two are combined using the log5 method into the higher seed's chance to win one game at a neutral site: (higher − higher × lower) / (higher + lower − 2 × higher × lower).
Home Field: worth 4%. The higher seed wins a home game at the neutral chance plus 4 points, and a road game at it minus 4. A best of 3 goes home–road–home; longer series open with two at home and two on the road, then alternate starting at home (2-2-1, 2-2-1-1-1, …). All higher seed puts every game in the higher seed's park.
Series: simulating every series until it is won. The first chart is the higher seed's chance to take a series of each length (a best of 1 is one home game); the second splits the chosen length by who wins and in how many games.
Data: runs scored, runs allowed, and games played from MLB's standings (StatsAPI).