Critical eye required: Four tips on how to recognize graphical data tricks 

We encounter charts and other graphically prepared data at every turn in our everyday lives. Since the beginning of the Corona pandemic, visual representations of current case numbers and developments have been omnipresent in the media. But such illustrations also play an important role in many other areas – be it for explaining election results or surveys, or for presenting statistics or research results.

However, such visualizations are not always immediately comprehensible nor is the message clearly evident – and sometimes messages are deliberately distorted. This makes it all the more important to interpret such diagrams, graphs and analyses correctly. Matthias Scherer, data expert and university lecturer at the FH Technikum Wien, has a few tips on how to recognize data tricks.

Scherer is a research specialist at the FHTW in the field of rehabilitation technology with a focus on motion analysis, prosthetics and biomechanics. In his doctoral thesis, he worked intensively on algorithms, statistical evaluations and data analysis. “When you want to interpret data and statements, you should always ask yourself these four questions. First, who is saying something and how does that person know? Second, where did the data come from and what is missing? Third, did someone change the context or subject matter? And fourth, does it make sense?” explains Scherer.

He is convinced that “reading data and graphs correctly is an art that can be learned. The most important thing is always to critically question what a person is trying to say and why the data is presented the way it is.”

Scherer illustrates this statement with a short fictional example. Two bar graphs show the percentage of coffee drinkers among students and employees.

The same data are shown on the left and right. However, the difference appears to be greater in the left representation, because here the axis has been tricked, while on the right the data are shown correctly (starting at 0%).

Such tricks and others are often used to make differences appear larger than they actually are. Scherer’s advice: “Stay critical and choose your information sources carefully!”

Source Note: Charts adapted from “How Charts Lie” – Alberto Cairo (2019).