First ask the right question: the data scientist edition
Book review: The Truthful Art by Alberto Cairo, and the Enduring Problem of Statistical Illiteracy

Football managers on the hot seat

Chris Y. asked how to read this BBC Sports graphic via Twitter:

Bbcsports_managers_winprecent

These are managers of British football (i.e. soccer) teams. Listed are some of the worst tenures of some managers. But what do the numbers mean?

The character "V" holds the key. When I first read the chart title, I wonder why managers are opposed to win percentages. Also, the legend at the bottom right confuses me. Did they mean "W" when they printed "V"? "Games W%" seems like a shorthand for winning percentage.

After looking up John Carver's not-so-impressive record, I learned that the left column are total number of matches managed and the right column is the winning percentage expressed as a number between 0 and 100.

I think even the designer got confused by those scales. Witness the little bar charts in the middle:

Bbcsports_managers_winpercent1

The two numbers are treated as if they are on the same scale. The left column is assumed to be the number of matches won while the right column is treated as the number of matches lost (or vice versa). Under this interpretation, the bar charts would depict the winning percentages. Let me fix the data:

Redo_bbcsport_managers

While these managers have compiled similar losing records on a relative basis, some of them lasted longer than others. The following chart brings out the difference in tenure while keeping the winning percentages: (I have re-sorted the managers.)

  Redo_bbcsports-managers-2

 When they finally got the sack, they reached the end of the line.

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