Trifecta checkup

147 posts
Simple charts are the hardest to do right

The CDC website has a variety of data graphics about many topics, one of which is U.S. vaccinations. I was looking for information about Covid-19 data broken down by age groups, and that's when I landed on these charts (link). The left panel shows people with at least one dose, and the right panel shows those who are "fully vaccinated." This simple chart takes an unreasonable amount of time to...

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What metaphors give, they take away

Aleks pointed me to the following graphic making the rounds on Twitter: It's being passed around as an example of great dataviz. The entire attraction rests on a risque metaphor. The designer is illustrating a claim that Covid-19 causes erectile dysfunction in men. That's a well-formed question so in using the Trifecta Checkup, that's a pass on the Q corner. What about the visual metaphor? I advise people to think...

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One of the most frequently produced maps is also one of the worst

Summer is here, many Americans are putting the pandemic in their rear-view mirrors, and gas prices are soaring. Business Insider told the story using this map: What do we want to learn about gas prices this summer? Which region has the highest / lowest prices? How much higher / lower than the national average are the regional prices? How much has prices risen, compared to last year, or compared to...

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Start at zero improves this chart but only slightly

The following chart was forwarded to me recently: It's a good illustration of why the "start at zero" rule exists for column charts. The poor Indian lady looks like a midget in this women's club. Is the average Indian woman really half as tall as the average South African woman? (Surely not!) The problem is only superficially fixed by starting the vertical axis at zero. Doing so highlights the fact...

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Finding the hidden information behind nice-looking charts

This chart from Business Insider caught my attention recently. (link) There are various things they did which I like. The use of color to draw a distinction between the top 3 lines and the line at the bottom - which tells the story that the bottom 50% has been left far behind. Lines being labelled directly is another nice touch. I usually like legends that sit atop the chart; in...

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Same data + same chart form  = same story. Maybe.

We love charts that tell stories. Some people believe that if they situate the data in the right chart form, the stories reveal themselves. Some people believe for a given dataset, there exists a best chart form that brings out the story. An implication of these beliefs is that the story is immutable, given the dataset and the chart form. If you use the Trifecta Checkup, you already know I...

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Circular areas offer misleading cues of their underlying data

John M. pointed me on Twitter to this chart about the progress of U.S.'s vaccination campaign: This looks like a White House production, retweeted by WHO. John is unhappy about this nested bubble format, which I'll come back to later. Let's zoom in on what matters: An even bigger problem with this chart is the Q corner in our Trifecta Checkup. What is the question they are trying to address?...

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Illustrating differential growth rates

Reader Mirko was concerned about a video published in Germany that shows why the new coronavirus variant is dangerous. He helpfully provided a summary of the transcript: The South African and the British mutations of the SARS-COV-2 virus are spreading faster than the original virus. On average, one infected person infects more people than before. Researchers believe the new variant is 50 to 70 % more transmissible. Here are two...

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Handling partial data on graphics

Last week, I posted on the book blog a piece about excess deaths and accelerated deaths (link). That whole piece is about how certain types of analysis have to be executed at certain moments of time.  The same analysis done at the wrong time yields the wrong conclusions. Here is a good example of what I'm talking about. This is a graph of U.S. monthly deaths from Covid-19 during the...

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Is this an example of good or bad dataviz?

This chart is giving me feelings: I first saw it on TV and then a reader submitted it. Let's apply a Trifecta Checkup to the chart. Starting at the Q corner, I can say the question it's addressing is clear and relevant. It's the relationship between Trump and McConnell's re-election. The designer's intended message comes through strongly - the chart offers evidence that McConnell owes his re-election to Trump. Visually,...

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