12-15-2014, 06:00 PM
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Mary Pat Campbell
SOA
AAA
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Join Date: Nov 2003
Location: NY
Studying for duolingo and coursera
Favorite beer: Murphy's Irish Stout
Posts: 90,450
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re the law school implosion:
http://byjustinfox.com/2014/12/14/th...ndamentalists/
Quote:
On Friday, I read a Natalie Kitroeff Businessweek.com story on the declining appeal of law school, and was so struck by this chart that I shared it on Twitter:
The chart tells a dramatic story: all the gains in law school enrollment since the mid-1970s have been wiped out in just three years. Twitter responded to that drama with lots of retweets and favorites — but also with lots of disapproving remarks like this:
[basically remarks about how bad the graph is because the vertical scale doesn't start at 0]
There were many, many more responses like that. A couple of them wielded the name of Edward Tufte, today’s leading authority on the visual presentation of data. Which is interesting, because after about five seconds of Googling I found Tufte’s actual views on the practice:
Quote:
In general, in a time-series, use a baseline that shows the data not the zero point. If the zero point reasonably occurs in plotting the data, fine. But don’t spend a lot of empty vertical space trying to reach down to the zero point at the cost of hiding what is going on in the data line itself. (The book, How to Lie With Statistics, is wrong on this point.)
For examples, all over the place, of absent zero points in time-series, take a look at any major scientific research publication. The scientists want to show their data, not zero.
The urge to contextualize the data is a good one, but context does not come from empty vertical space reaching down to zero, a number which does not even occur in a good many data sets. Instead, for context, show more data horizontally!
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Such arguments seem to carry little weight, though, among the legions of what BuzzFeed’s Matthew Zeitlin has dubbed y-axis-zero fundamentalists. I had somehow missed out on their rise, I guess because all of my HBR time-series charts over the past few years have for various reasons (the main one being that my Excel skills are so limited that I don’t know how to truncate the axes) featured y-axes that go to zero. But apparently now this is a thing. The Huffington Post‘s Ben Walsh reported a similar experience with a recent (non-zero-based) chart on taxi medallions in New York. According to Walsh, “all the responses were like ‘rule violated. i refuse to consider your thesis’.”
When I checked the Twitter bios of the people who objected to Businessweek.com chart, most of them were software programmers, so I wondered if it was some weird coder obsession. It might be, but a simpler explanation was that prominent programmer Jeff Atwood had retweeted it to his 152,000 followers.
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The Businessweek.com chart, on the other hand, was crafted to show the data as fully as possible. Facebook “data visualization guru” Andy Kriebel recommends adding a note to any non-zero-based-y-axis chart explaining why you didn’t base it at zero. That’s not a bad idea, but I also think the overwhelming majority of those who read a chart like this one online (as opposed to those who see a chart flitting by on the TV screen) are able to figure out what’s going on. I love that so many people online are on the lookout for dodgy charts. But focusing on the data isn’t really dodgy.
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I rarely include 0 in my axes, where it's not relevant. |
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