Name: 【TED-Ed】How to spot a misleading graph - Lea Gaslowitz
Uploaded: 2017-08-10T01:32:47.000Z
Duration: 4 min 10 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

A toothpaste brand claims their product will destroy more plaque

A politician tells you their plan will create the most jobs.

We're so used to hearing these kinds of exaggerations

But what about when the claim is accompanied by a graph?

It represents cold, hard numbers, and who can argue with those?

Yet, as it turns out, there are plenty of ways graphs can mislead

In this 1992 ad, Chevy claimed to make the most reliable trucks in America

Not only does it show that 98% of all Chevy trucks sold in the last ten years

but it looks like they're twice as dependable as Toyota trucks.

That is, until you take a closer look at the numbers on the left

and see that the figure for Toyota is about 96.5%.

If it went from 0 to 100, it would look like this.

This is one of the most common ways graphs misrepresent data,

Zooming in on a small portion of the y-axis

exaggerates a barely detectable difference between the things being compared.

And it's especially misleading  with bar graphs

since we assume the difference in the size of the bars

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

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

These techniques are known as cherry picking.

A time range can be carefully chosen to exclude the impact of a major event

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.

because while the number  of football fans has increased,

their share of overall viewership has not.

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

But in fact, a rise of even half a degree Celsius

which show the average temperature variation each year,

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.

and ask what story the picture is trying to tell.

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【TED-Ed】How to spot a misleading graph - Lea Gaslowitz

relevant

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massive

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