Long odds: What was the probability of the visiting team winning every World Series game?

For the first time ever, every World Series game was won on the road: the Astros won all three of their away games, while the Nationals came out on top winning their four away games. Although there is a positive probability of the visiting team winning each game, when we look at the chances of the visiting team winning every game of the World Series are very small. Since the World Series began in 1903, we have not seen the visiting team win all seven of the games to decide the championship. What are the odds? 

Let’s begin by taking each team’s winning record on the road. The Nationals won 43 of their 81 road games in the 2019 season, giving them a winning percentage, which we will call N, of 53.09%. The Astros won 47 of their 81 road games in the 2019 season, giving them a winning percentage, which we will call A, or 58.02%. So, based off the teams’ winning record on the road for the regular season, the probability that the visiting team would win each game of the World Series is (N4)(A3) since the Nationals won 4 games on the road, while the Astros won 3. This works out to a 1.7% probability that every game for the 2019 World Series was won by the visiting team, based off the on the road record of each team in the match up. Basically, this means we could expect this to happen between one and two times every hundred years. So, since we hadn’t seen this in over a hundred years, it’s almost like the inevitable finally happened.  

Now, this was the World Series – when the two best teams in baseball face off. So maybe the winning percentage on the road for the regular season isn’t all that representative of winning in the championship games. Let’s look at data since 1995 since this is when the Wild Card play-in game began in Major League Baseball. During that time, 63 of the 140 World Series games have been won by the visiting team. So, we can take the probability that the road team will win a World Series game, which we will call T, is 0.45. For every game in the World Series to be won by the visiting team, the series must go to seven games. Using this formulation, the probability that the visiting team will win every game of the World Series is T7, or 0.37%. This can be interpreted as about once every 300 years. 

Are you surprised that only the visiting team won in the 2019 World Series? Odds appear to be in your favor that we saw an anomaly and a series for the ages!

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