In-Class Activity #10: Correlation between Team Rank and Wins

Background

In 2012 and 2013, there were 10 teams in the MLB playoffs: the six teams that had the most wins in each baseball division, and four “wild card” teams. The playoffs start between the four wild card teams - the two teams that win proceed in the playoffs (8 teams remaining). Then, these teams are paired off and play a series of games. The four teams that win are then paired and play to determine who will play in the World Series.

We can assign rankings to the teams as follows:

• Rank 1: the team that won the World Series
• Rank 2: the team that lost the World Series
• Rank 3: the two teams that lost to the teams in the World Series
• Rank 4: the four teams that made it past the wild card round, but lost to the above four teams
• Rank 5: the two teams that lost the wild card round

teamRank <- c(1, 2, 3, 3, 4, 4, 4, 4, 5, 5)
teamRank

##  [1] 1 2 3 3 4 4 4 4 5 5

2012 Regular Season Wins

In 2012, the ranking of the teams and their regular season wins were as follows:

• Rank 1: San Francisco Giants (Wins = 94)
• Rank 2: Detroit Tigers (Wins = 88)
• Rank 3: New York Yankees (Wins = 95), and St. Louis Cardinals (Wins = 88)
• Rank 4: Baltimore Orioles (Wins = 93), Oakland A’s (Wins = 94), Washington Nationals (Wins = 98), Cincinnati Reds (Wins = 97)
• Rank 5: Texas Rangers (Wins = 93), and Atlanta Braves (Wins = 94)

wins2012 <- c(94, 88, 95, 88, 93, 94, 98, 97, 93, 94)
wins2012

##  [1] 94 88 95 88 93 94 98 97 93 94

Exercise 1: Correlation between teamRank and wins2012

cor(teamRank, wins2012)

## [1] 0.3477129

2013 Regular Season Wins

In 2013, the ranking of the teams and their regular season wins were as follows:

• Rank 1: Boston Red Sox (Wins = 97)
• Rank 2: St. Louis Cardinals (Wins = 97)
• Rank 3: Los Angeles Dodgers (Wins = 92), and Detroit Tigers (Wins = 93)
• Rank 4: Tampa Bay Rays (Wins = 92), Oakland A’s (Wins = 96), Pittsburgh Pirates (Wins = 94), and Atlanta Braves (Wins = 96)
• Rank 5: Cleveland Indians (Wins = 92), and Cincinnati Reds (Wins = 90)

wins2013 <- c(97, 97, 92, 93, 92, 96, 94, 96, 92, 90)
wins2013

##  [1] 97 97 92 93 92 96 94 96 92 90

Exercise 2: Correlation between teamRank and wins2013

cor(teamRank, wins2013)

## [1] -0.6556945

Conclusion

The correlation between teamRank and wins2012 is positive but not that strong. This suggests that in 2012 the regular season wins were only loosely related to how far a team advanced in the playoffs. On the other hand the correlation between teamRank and wins2013 is negative and relatively strong. Thisindicates that in 2013 teams with more regular season wins tended to achieve a better playoff rank. This illustrates that a team’s regular season win total is not always a reliable predictor of postseason success.