epeters:graphs

How to spot a misleading graph (Vol.2)

A toothpaste brand claims their product will destroy more plaque than any product ever made. A politician tells you their plan will create the most jobs. We’re so used to hearing these kinds of exaggerations in advertising and politics that we might not even bat an eye.

But what about when the claim is accompanied by a graph? After all, a graph isn’t an opinion. It represents cold, hard numbers, and who can argue with those? Yet, as it turns out, there are plenty of ways graphs can mislead and outright manipulate. Here are some more things to look out for.

Our last post on reading graphs discussed how bar graphs can be manipulated to mislead you, but the scale can also be distorted along the x-axis, usually in line graphs showing something changing over time. This chart showing the rise in American unemployment from 2008 to 2010 manipulates the x-axis in two ways.

First of all, the scale is inconsistent, compressing the 15-month span after March 2009 to look shorter than the preceding six months. Using more consistent data points gives a different picture with job losses tapering off by the end of 2009. And if you wonder why they were increasing in the first place, the timeline starts immediately after the U.S.’s biggest financial collapse since the Great Depression.

These techniques are known as cherry picking. A time range can be carefully chosen to exclude the impact of a major event right outside it. And picking specific data points can hide important changes in between. Even when there’s nothing wrong with the graph itself, leaving out relevant data can give a misleading impression.

This chart of how many people watch the Super Bowl each year makes it look like the event’s popularity is exploding. But it’s not accounting for population growth. The ratings have actually held steady because while the number of football fans has increased, their share of overall viewership has not.

Finally, a graph can’t tell you much if you don’t know the full significance of what’s being presented. Both of the following graphs use the same ocean temperature data from the National Centers for Environmental Information. So why do they seem to give opposite impressions? The first graph plots the average annual ocean temperature from 1880 to 2016, making the change look insignificant. But in fact, a rise of even half a degree Celsius can cause massive ecological disruption. This is why the second graph, which show the average temperature variation each year, is far more significant.

When they’re used well, graphs can help us intuitively grasp complex data. But as visual software has enabled more usage of graphs throughout all media, it’s also made them easier to use in a careless or dishonest way. So the next time you see a graph, don’t be swayed by the lines and curves. Look at the labels, the numbers, the scale, and the context, and ask what story the picture is trying to tell. 

Check out Volume 1!

From the TED-Ed Lesson How to spot a misleading graph - Lea Gaslowitz

Animation by Mark Phillips

youtube

The state of gun violence in the US, explained in 18 charts

This week has been decently productive so far! Which is easier to visualize now that I updated these charts in my Google Sheet. Particularly the relative weekly totals in the donut chart. Capstone should always be the biggest chunk of the donut, but the point of including this chart was more so to make sure I am doing a little bit of everything each week, and to eventually track the trends. (I spent too much time fussing with this spreadsheet this week, tbh.)

I have blocked social media and trained myself to not feel an urge to check it. I think I might just completely block it even longer so I can only access it on campus computers (which I don’t want to do for long in case anyone sees). Maybe only do a weekly update on Fridays or something.

Life is more peaceful without feeling the need to be connected all day long. It’s a nice breath of fresh air.

But anyway. I got a bit behind this past weekend because I forgot I took on extra work shifts. So this weekend should be much more productive. I’m hoping to meet all my coursework hour goals this weekend to start fresh with an even more productive week the next!

shitty internet == hard for me to tell what says in background

Pie chart: People who are eat a healthy diet.   People who are thinking of eating pie now. 

Tic tac toe of Mr. Peanutbutter vs Woodchuck.

Bar graph of Winner vs Loser.

Chart on right blue line is voters concerns and red line is issues addressed.

Also for anyone outside of the U.S., the red white and blue portrait of Mr. Peanutbutter is a reference to the iconic painting of Obama during his campaign in 2008. It got so big that Pepsi changed their logo to make it look similar.

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Guys, this was so fun, thank you!!

I had 111 responses. :3

The overall pattern was… actually pretty close to the feel I had for it in my head! That’s neat.

The average age was 25.9 and the median was right about the same–25.

If you’re not used to boxplots, that one on the right shows the distribution of ages by quartiles (followers divided into four even groups.)  So 50% of my followers are between 20.5 and 29.5 (with 25 the division between the two middle quarters).  Another quarter were over 29, and a quarter were 20 and under.

Other interesting notes:  Obviously gonna be some self-reporting and selection bias.  Also effects of time/days I posted requests? 

For example, all but one of my handful of <18 answers showed up this afternoon.  (PS: hi, y’all are welcome, but please mind the nsfw tags, tread with care, and if you encounter anything that makes you uncomfortable check in with an adult you trust.  I talk about bug sex and weird dick trivia, like…. way too much to have any idea as to the appropriateness of this space.)

The most common response was 22, by a landslide, and the runner up was 32, which is my age, hello my cohort, we appear to have eaten the majority of our neighbors. >:33