
The public do not understand logarithmic graphs used to portray Covid-19 - ingve
https://blogs.lse.ac.uk/covid19/2020/05/19/the-public-doesnt-understand-logarithmic-graphs-often-used-to-portray-covid-19/
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vharuck
Some of the comments at the bottom of the article lament the "innumerancy" of
the general public. But let's be honest: logarithmic scales take effort to
read. And like any kind of communication, you should make it easy to read.

As a person who creates and looks at charts all day, I can read complex
charts. But I really prefer other people use linear charts of simple bars or
trend lines. You're conveying a new idea to me, so don't assume I have all the
context you do when reading the chart.

If you want to show acceleration, remember to use different units. Choose a
unit that can be shown on a linear scale. E.g., the ratio of today's cases
over the cases from a week ago.

~~~
mytailorisrich
Well log scale is intended to make it easier to read... In general it is used
in cases where a linear scale would be unreadable.

Your suggestion about changing what is represented in order to avoid a log
scale is good but does not solve the root of the issue: many members of the
public will not understand the information however it is represented because
the concept itself is too complex.

It really is a numeracy problem.

~~~
redis_mlc
Blaming the people you're trying to communicate with is not a winning move.

When you look at the 2 graphs side-by-side, as in the article, it's apparent
which conveys more meaning (the linear one), unless I suppose you read log
graphs all day. The public does not.

~~~
mytailorisrich
Blaming would be to claim that it is their fault for not understanding. Here
it is not blame, it is a statement that anything above the most basic maths
concepts will stump a surprisingly large number of people. I'm not sure
'surprisingly' is the right word but here it is.

------
pjdorrell
It's not just a matter of not understanding, it's also the tendency to assume
the default, which is a linear scale.

One suggestion would be to make the logarithmic scale super-obvious and in
your face.

"1 10 100 1k 10k 100k" in small print obscures the unusual nature of the
scale.

Instead, show 1 10 100 1000 10000 100000 and show those numbers in a large
bold font so that they are the most noticeable feature of the graph.

(Possibly use an increasing font size.)

~~~
muzika
Best log charts I seen had a linear version of the chart next to it, or one
visible by toggling a UI option.

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thisrod
This is propaganda.

What actually happened? Some people were shown linear data on a linear scale,
others were shown the same linear data on a logarithmic scale. The people who
saw a straight line, because the scale matched the data, were better able to
interpret and extrapolate the data.

The spread of the novel coronavirus in the USA _used_ to be exponential, but
it was linear at the time the subjects were asked to analyse.

You don't say! Before the the authors recruited 2000 subjects to investigate
that, maybe they could have enrolled in Physics Practical 101 and listened to
the demonstrator. If they went to an old-school physics department, they would
have seen some real semi-log graph paper, designed for people to read actual
values off. It doesn't look anything like the scales on their graphs.

Oh, but the subjects who saw a linear graph were more likely to accept the
authors' opinion on what to do about that data.

The authors are right: the USA and UK should do more to contain the
coronavirus. But it's still propaganda to advocate that data be presented in a
certain format because that makes readers agree with your opinion, even when
your opinion is right.

~~~
shaftway
> [...] we find that the group who read the information on a logarithmic scale
> has a much lower level of comprehension of the graph: only 40.66% of them
> could respond correctly to a basic question about the graph (whether there
> were more deaths in one week or another), contrasted to 83.79% of
> respondents on the linear scale.

> Admittedly, we cannot know which policy preferences are superior. However,
> we do know that unlike the people who saw the graph on a logarithmic scale,
> the people exposed to a linear scale graph can form their preferences based
> on information that they can understand better.

While they're using pandemic data, they're asking people about their basic
understanding of data in the graph.

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redis_mlc
It's a good article - everybody should read it.

> The public do not understand logarithmic graphs used to portray Covid-19

\- does the public include our leaders? Very likely.

\- although I know what a log plot is, I didn't have an intuitive answer to
the question posed in the article. So instead of informing people, it adds
further confusion.

Related:

\- the Santa Clara (Bay Area) hospitals dashboard is confusing and takes about
2 minutes to load, so another example of poor crisis communications -
inexcusable in 2020:

[https://www.sccgov.org/sites/covid19/Pages/dashboard.aspx#ho...](https://www.sccgov.org/sites/covid19/Pages/dashboard.aspx#hospital)

If anybody is familiar with that BI software, is there a way to cache it?

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craftinator
Logarithmic scales are such a common and useful tool, it's a hard pill to
swallow that the general populace doesn't have the knowledge or interest to
understand them. I'm not talking from an elite academic point of view; if you
make it through sophomore year of high school, you have at least been exposed
to them, and if you graduate highschool you've been tested on their use.

I use them regularly (nearly every time I plot data to figure out trends or
whatever), and have a hard time imagining not having them for problem solving.

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jobigoud
I love log graph but I understand the sentiment.

Yesterday I was looking at a COVID-19 log graph and I was interested in a
point of the curve right at the middle between the 100 and the 1000 tick mark.
It's hard to have an intuition on what the value was.

edit: I double checked for the record, the value halfway between 100 and 1000
is 316.2.

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alanlamm
The financial times has a covid tracker with log vs linear, daily vs
cumulative and absolute vs per capita toggles. I understand log scales and
even so, changing these settings really makes me look at the data differently.
For example - look at absolute daily data on a log scale and Brazil seems
headed for destruction, overtaking the UK amd US. Look at cumulative per
capita data on a linear scale and things don't seem so bad for Brazil, but
Belgium looks like a disaster.

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Isamu
Well even tech folk don’t read charts correctly, even if they understand a
logarithm.

I have seen all kinds of junk nonsensical charts in my career that somehow
made it into reports, because nobody thought it was necessary to take the time
to READ the chart and ask a few questions to see if it made any sense.

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math1234321
I made a video about this for my students. Basic math behind a NYT graph
[https://www.youtube.com/watch?v=w2--
cCFwSbA](https://www.youtube.com/watch?v=w2--cCFwSbA)

