In-Class Activity #10 — Correlation Between Team Rank and Wins

Question

Playoff teams are ranked 1 (World Series winner) through 5 (lost the wild-card round). Using the given rank vector, build the 2012 and 2013 regular-season win vectors in rank order, then compute the correlation between team rank and wins for each year.

Set up the vectors

# Rank of each of the 10 playoff teams (1 = champion ... 5 = lost wild-card round)
teamRank = c(1,2,3,3,4,4,4,4,5,5)

# Regular-season wins in rank order, 2012
wins2012 = c(94,88,95,88,93,94,98,97,93,94)

# Regular-season wins in rank order, 2013
wins2013 = c(97,97,92,93,92,96,94,96,92,90)

Correlation for 2012 (Exercise 1)

cor(teamRank, wins2012)

[1] 0.3477129

Correlation for 2013 (Exercise 2)

cor(teamRank, wins2013)

[1] -0.6556945

Answers

• Exercise 1: cor(teamRank, wins2012) = 0.3477129
• Exercise 2: cor(teamRank, wins2013) = -0.6556945

A lower rank number means a better playoff finish (rank 1 = champion), so a negative correlation means “more wins → better finish.”

In 2012 the correlation is positive (+0.35), while in 2013 it is negative (-0.66). Because the two years point in opposite directions, there is no consistent relationship between regular-season wins and playoff success. Regular-season win totals are not a reliable predictor of who advances in the playoffs, so we wouldn’t feel comfortable betting on the postseason based on this data.