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Posts Tagged ‘Bar chart’

Have data graphics progressed in the last century?

01 Mar

Received a wonderful link via reader Lonnie P. to this website that presents a historical reconstruction of W.E.B. DuBois's exhibit of the "American negro" at the 1900 Paris Expo. Amusingly, DuBois presented a large series of data graphics to educate the world on the state (plight) of blacks in America over a century ago.

You can really spend a whole afternoon examining these charts (and more); too bad the charts have poor resolution and it is often hard to make out the details.

***

Judging from this evidence, we must face up to the fact that data graphics have made little progress during these eleven decades. Ideas, good or bad, get reinvented. Disappointingly, we haven't learned from the worst ones.

Exhibit A 

  Dubois_a

(see discussion here)

Exhibit B

Dubois_b

 (see discussion here)

Exhibit C 

  Dubois_c

(See discussion here.)

Exhibit D

Dubois_dd
 (see the Vampire chart here)

Exhibit E

Dubois_e
(see the discussion here.)

Exhibit F

Dubois_f
(see discussion here.)

 
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The richness of nothingness

15 Dec

Statisticians investigate data, and it may seem like missing data should be ignored since no data means no analysis, right? Well, in practice, it turns out that the knowledge that data is missing is very powerful, and statisticians are, in fact, always wary of missingness.

Dailykosbloomberg A reader pointed me to Daily Kos for another chart which I'll eventually talk about -- but I got waylaid by this one (shown on the right), depicting the relative proportions of favorable and unfavorable ratings for a set of political players.

The data is simple, and the chart is sufficient although I'd avoid the blue/red coloring which connotes party affiliation in American politics. The graph also fails our self-sufficiency test.

But really, the big problem with this chart is not on the page. Alert readers might realize that very few people (in fact, only just over half) have an opinion of John Boehner.

In the following version, the proportion of missing/no opinion/don't know is plotted right beside favorables and unfavorables, revealing that this proportion ranges wildly from only 4% for Obama and Bush to 48% for Boehner.

Redo_fav1 This is one data set which makes stacked bar charts look better than they typically are. The two main categories of favorable and unfavorable can be stacked to the sides so that they can individually be compared. The middle part, which represents missing data, will usually not provide much information but in this dataset, the gaping blank space makes us think about how we should treat the missing data.

In this chart, we give equal weight to those who have an opinion and those who don't.

***

Alternatively, we could ignore the people with no opinion, and look at the proportion of favorables and unfavorables among those who have an opinion. There is a danger in doing this because as seen above, the large proportion of don't knows would be hidden from view, and in the case of Boehner, and even for Pelosi and Tea Party, the amount of missing raises interesting questions: have people not heard of these players? are they afraid of providing an opinion? are they conflicted? etc.

Here is the alternative view, in which I have added a couple of comments to highlight things that otherwise would have been missed. One notable feature is that the respondents in this survey essentially view most of these players in similar light (40-50% favorable), as I don't see the differences in the center of the chart as meaningful.

Redo_fav2

 

 
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Posted in Google Reader, Politics