[OC] How to spot misleading charts? I would like to hear your opinion on the subject, also any tips design-wise?
Submitted by dark_o3 t3_zg7pck in dataisbeautiful
Wrongly scaled Y axis are the thing I see most often.
The problem is that in some plotting programs that's the default. That's why it's hard to know if the journalist presenting the graph is deliberately trying to mislead or is just incompetent and doesn't understand that if he/she doesn't tell the plotting program not to suppress zero, the graph will be misleading.
Criminally negligent or just criminal.
Journalists should know this, it’s not complicated. Assume intent to mislead. Or that they’re too dumb to be doing their job.
Halon’s Razor would like a word.
“Never attribute to malice that which can be adequately explained by stupidity.”
But my article is more convincing if the difference looks bigger.....i feel like the difference is this big...
I wonder if there is room for some journalism exam that requires passage. How to properly display data, etc. It wouldn't have to be exceptionally complicated but I think there are zero entrance requirements to being a journalist. At least you could say 'certified' or some such. Maybe there is qualification exam out there I don't know of.
I think we need less official credentials, really. No reason why hair dressers need a license. But newspapers shouldn’t hire journalist, people who deal in fact finding, if they are easily deceived.
Not every graph needs to start at 0 though. A graph of temperature, for example, shouldn't ever start at 0 K unless you're dealing with temps in that range.
I agree that there are a few exceptions, temperature being one of them. However, most misuse of suppressed zero is not with these quantities.
I think there are good reasons to cut a y axis short, but you have to know your audience. If there are small differences, but you want to draw attention to those differences, it can make sense. I've done it in academic papers before, comparing scores in one group around 80% and scores in the other group around 87%. Statistically significant, but the full-scaled graph just doesn't present that information clearly. Scientists can handle looking at the y axis to check, but your everyday person likely won't.
Maybe it's not always intentional, but as journalists they have an obligation to do it right.
There are instances where starting the Y-axis not at zero is okay. I'm bad at examples, but zero is used as a baseline. Which means that it would be better to start the Y-axis at another value, it being similar to the baseline.
An example might be the concentration of something, like CO2 molecules in the atmosphere. It is impossible and irrelevant to get to 0. Besides, it's not about the absolute values but the relative values.
But in general, yeah, it is misleading.
Temperature is another one. Unless you're doing experiments at absolute zero, 0 degrees K shouldn't be on your graph.
It's often true if you want to show the differences between similarly (usually large..) numbers. Whether it is misleading or not tends to be in the presentato and context. The same applies to things like log scales etc...
The moment you compare those temperature, either in graph or in percent, you need to switch to K first.
10°C is not half as cold as 20°C
For my data presentation it's usually only okay to start above 0 when doing so would make it hard or impossible to see necessary details in the plot.
By wrongly scaled you mean starting with a value different than zero? Because they are very different things
You see it a lot on scientific papers, it was more common before but you do still have a few papers that come out with a badly scaled Y axis to insist on the difference between group A and group B.
In scientific papers they'll generally have some measure of variance, and a readership that knows how to interpret it.
You didn’t answer their question: they asked about zero as the baseline.
What’s so special about zero?
It's usually less about what the starting Y value is as it is about the scaling for the overall data, coupled with a plot point to close to the starting y value.
I mean, people should be able to critically think through this, but if that were the norm, we would probably have flying cars robot slaves better living conditions less bullshit to deal with.
On a scale of 9.5 to 10 how annoying is that?
It depends - is it a log scale?
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