Working with lines

Much data, zero info

The number crunching college football fans at the Wall Street Journal wondered out loud:

One of the biggest developments in college football in recent years was the decision by Virginia Tech and Miami -- perennial top-20 teams -- to leave the Big East conference and join the Atlantic Coast Conference.  How much has that strengthened the ACC?

Wsj_accThe data table on the right was ostensibly the answer.  Readers were drawn to the bolded numbers, the almost identical winning percentages of ACC and SEC (averaged over the last decade, as the text explained).

The question is a classic one of cause and effect: did the addition of two strong teams cause the ACC to become stronger?  Startlingly, the data cited was useless, and the analysis conducted irrelevant.

First, the difference in winning percentages between ACC and SEC is the wrong metric.  Something more pertinent is, for example, the change in winning percentage of ACC before and after the team additions.

Second, the observation period is seriously mistaken.  The ACC expansion occurred in 2004 so average winning percentages from 1995-2005 have zilch to say about its effect.

Third, a Web search uncovers that major realignment occurred again in the ACC in 2005, making it very difficult to isolate the effect of adding Virginia Tech and Miami in 2004.

Thus, the data table contains zero information for addressing the stated problem.  How to measure the effect properly seems to me a tall order, and a good discussion topic.

Besides the iffy statistics, it is also impossible to read this table.  The data in the lower left triangle is a reflection of those in the upper right triangle, containing no new information.  Head-to-head conference comparisons seem to serve no purpose.  Actual win-loss numbers create clutter while adding no insight.  (Theoretically, the larger the number of contests between any two conferences, the more reliable are the winning percentages.  Confidence intervals is a much better way to present such information but even those would be over-kill for our purpose.)

Reference: "College Football's Power Struggle", Wall Street Journal, Sept 16-17, 2006.


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Jeremiah McNichols

You're the Simon Cowell of analytics!

Seriously - thanks for nailing this one to the wall. The worst charts often provide the fullest opportunities for discussion.

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