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Which Big Ten Division is Better?

Big Ten LogoAfter another round of what seems like endless conference realignment, the Big Ten has settled on 14 teams split into two divisions; East and West. However, with the likes of Ohio State, Penn State, Michigan, and Michigan State, the East division appears to be much stronger. In fact, Indiana athletic director Fred Glass called it the “Big Boy Division,” and Penn State coach Bill O’Brien referred to it as “Murderers' Row.”

But will the statistics back up their claims? After all, it’s easy to spout off any opinion you want. I could claim that the Sun Belt is a better football conference than the SEC.  But without any kind of data analysis to back up my opinion, it’s meaningless. So before we go claiming that the East division is going to dominate the West for years to come, let’s see if the statistics agree.

The Data

I collected the conference winning percentage of every Big Ten team over the last 10 years. I stuck with only conference games because the non-conference schedule can vary a great deal from team to team. Sticking with only conference games gives us a similar sample of games for each team. Of course, Maryland, Rutgers, and Nebraska didn’t all play in the Big Ten for the last 10 years. But Big East jokes aside, their conferences really weren’t that different from the Big Ten. Plus, it’s not like Rutgers and Maryland were dominating the Big East and ACC. So for the purposes of this data analysis, we’ll use their record from their respective conferences.

But winning percentage doesn’t always tell us everything. Last year Michigan State was 3-5 in the Big Ten, but that was because they went 2-5 in Big Ten games decided by 4 points or less. On the season, they actually scored more points against conference opponents (159) than they allowed (149). Compare that to Purdue, who also had a conference record of 3-5, but scored 189 points while allowing a whopping 265. So despite having the same conference record, Michigan State was really a better team than Purdue last season because they had a higher scoring differential. Because of this, I’m going to use scoring differential along with winning percentage to compare the two divisions.

You can download a Minitab worksheet with the data in it here. I invite you to open Minitab (or download a free 30-day trial version if you don't already have it) and follow along!

Comparing Winning Percentage

Taking the winning percentage of all 14 Big Ten teams over 10 years gives us 140 observations. I split them up into two groups (East and West) and used Minitab Statistical Software to run a 2-Sample t analysis on the data.

Minitab's 1-Sample t Analysis

Boxplot

We see that the winning percentages for both divisions are about 0.500. The East is a little higher at 0.516 compared to 0.476 for the West. But the p-value of 0.35 is not less than 0.05, meaning that the difference is not statistically significant. The boxplot clearly shows that there really isn’t a big difference in the winning percentages between the two divisions over the last 10 years.

But we already stated that winning percentages don’t always tell the full story. So will we get a different result if we use scoring differential instead?

Comparing Scoring Differential

Just like above, I split the scoring differentials for each team into two groups and used Minitab to perform a 2-sample t analysis.

Minitab's 1-Sample t Analysis

Boxplot

Over the last 10 years, teams in the Eastern division have outscored their conference opponents by an average of 7 points per season while teams in the West have been outscored by 10.3 points. However, the p-value is 0.244, which again means there is not enough evidence to conclude that this difference is statistically significant.

And for fun, if you’re wondering which team is the outlier on the Boxplot, it’s the 2005 Illinois team, which was outscored by 257 points over 8 Big Ten games. Included in those games was a 61-14 loss to Michigan State, a 63-10 loss to Penn State, and a 40-2 loss to Ohio State. Ouch!

But back to the data analysis. It’s usually a good idea to determine the reason (if there is one) why you reach your conclusions. In this case, is there a specific reason why we can’t conclude there is a difference between divisions? To do this, let’s break down the data by team. The table below shows how each team ranks over the past 10 seasons in scoring differential per season.

Rank

East Team

Scoring Differential

West Team

Scoring Differential

1

Ohio State

110.4

Wisconsin

70.6

2

Penn State

46

Iowa

28.8

3

Michigan

39.8

Nebraska

12.6

4

Michigan State

13.2

Purdue

-17.1

5

Rutgers

-3.1

Northwestern

-36.4

6

Maryland

-27.8

Minnesota

-52.6

7

Indiana

-129.3

Illinois

-77.9

 
Comparing similarly ranked teams, you’ll see that the East Team is higher than the West Team in every case, minus one. Over the last 10 seasons, Indiana has been outscored by 129.3 points each season! That’s 51 more points than the last place team in the West Division! And do you know how many wins Indiana has over Eastern Division teams in the last 10 years? ONE! They just have a single win over Michigan State in 2006! In Indiana’s defense, they didn’t get to play Rutgers or Maryland. But still, things don’t look good for the Hoosiers moving forward.
 
So is Indiana the only thing keeping us from concluding that the East Division is in fact “Murderers' Row”? We can remove both Indiana and Illinois (the last-place teams) to find out.

Minitab's 1-Sample t Analysis

Boxplot

Without Indiana, the Eastern teams now have a scoring differential of 29.8. The West only rises to a scoring differential of 1 without Illinois. And this time the difference is statistically significant, since the p-value is less than 0.05. You can also see in the boxplots how the East has higher values for scoring differentials while the West has much lower values.

So Is the East Division Really Murderers' Row?

We cannot conclude that “top to bottom” the East Division is better than the West Division. Because Indiana has led the Big Ten in futility the last 10 years, there isn’t a significant difference in the winning percentages or scoring differentials between the two divisions. But what if you’re just talking about the teams at the top? We’ve shown that without the cellar dwellers, the East is in fact better than the West. Based on the last 10 years, I’d much rather play the top teams in the West than the top teams in the East.

But the fun part about sports is that the next 10 years aren’t going to be the same as the last 10. There are so many unanswered questions that will affect the competitiveness of each division. Will Wisconsin continue to remain an elite team without Brett Bielema? Can Penn State stay competitive throughout their period of sanctions? How will Rutgers and Maryland adjust to playing in the Big Ten? Will Indiana get a division win in the next decade?

But Hoosier jokes aside (c'mon, they’re just so easy!) this statistical analysis has shown that the top teams in the East do appear to have an edge over the top teams in the West. Whether that edge will persist going forward remains to be seen. Yes, the East Division may be up 7-0, but the game has just begun!

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