[benfle]

The author is obviously more interested in telling entertaining stories (in the boardroom) than telling the truth.

Tufte is not only about data viz. and powerpoint bashing. Integrity is central to his work.

I would not trust someone who present me a graph like in the second example (whether as a pie chart or as a bar chart). There is no way to know if the classes have the same attendance. Hence his conclusions could be completely wrong.