The histogram is Australia WhatsApp Number List the most used form of dataviz in our presentation materials. The access to all icon graphics functions of the office suite is also precisely a histogram: . This form of representation makes it possible to illustrate time series, to highlight the preponderance of causes in the explanation of a phenomenon, to break down variables by groupings, etcetera etcetera. The histogram is a powerful representation because it allows to gauge at a glance the values ​​of each series of data and especially to compare each series between them. In other words, we are used – even determined

to derive two things from the rapid reading of a histogram: information in absolute value and information in relative value (comparison of data series). So let’s take the graphic from Ms. Vidal’s tweet: In a context where our attention span is shrinking, on a social network like Twitter, I can only imagine that a significant portion of the readers of this tweet will have been guided by the natural inclination to capture information. that the histograms immediately offer, in this case: an absolute value on the number of students admitted to the second year of medicine each year, and information in relative value on the evolution of this value over time.

To truncate is to fake

But here, the y-axis is truncated . And it is so well truncated that by reading it like a cookie, the inattentive innocent will understand that the number of students admitted to the second year of medicine has multiplied by ~ 10 in 11 years! This is what the relative size of the bars suggests at first glance, or in any case, it is the information that we derive most naturally from them . In fact, this number has increased by 44% over the period … I imagine that is already good, but it is not x10 either. Once corrected, the histogram no longer has the same impact, yet it is the right-hand version that Ms. Vidal should have favored:

This “truncation” may seem anecdotal but graphic representations are used precisely because they mark the reader, they must simplify their access to forms of abstraction, more or less complex concepts: these representations, whether they like it or not. no, help shape our imagination, solidify our knowledge and build our mental models. In your Excel, your Powerpoint or your Tweets, do your audience a favor, don’t cut off your axes! Did you get good? If not, this is normal: past 1 dimension, we are not very good at evaluating the relative size of the objects around us *. Do you remember the Big Deal? This game show hosted by Vincent Lagaffe and where a test consisted in seeing a guy struggling to guess which container could contain


precisely a volume of liquid from another container? If so, it is exactly the same principle. If not, I’m going to question myself a little … the volume of a double ball when its radius is multiplied by the cubic root of 2 (~ 1.26), the area of ​​a double circle when its radius is multiplied by the square root of 2 (~ 1.41) If I speak to you about the Big Deal and bowling balls with passion, it is because it has to do with our subject. We have certainly all seen one of these types of graphics in a meeting: These graphs all have in common that they offer data representations in more than one dimension. Note that they also all have in common that they are more or less incomprehensible:

1 dimension is nothing

Powerpoint is a powerful tool precisely because it promotes the schematization and prioritization of our ideas. As for the graphic representations, the Powerpoint support must, therefore, facilitate the understanding of your messages by the audience. Structuring in bullet points, font size / formats, diagrams, slide titles… all this contributes to this. But pushed to the limit, the use of these functionalities can produce precisely the opposite effect: important messages embedded in the slide, prioritization of ideas by bullet points at 20 unreadable levels, information too condensed and unclear, etc.

These are the effects that were observed in the “deadly” Slide by the experts in charge of investigating the Columbia shuttle crash. This slide was part of a larger presentation dealing with the risks identified by the Boeing teams and linked to the damage suffered by the shuttle during its take-off. We find there the mention of the risk induced by the impact of the piece of insulating foam against the wing of the machine on takeoff: it was 640 times larger than those used for the impact resistance tests. And yet, the report of the investigation committee underlines that by reading the incriminated slide “it is easy to understand how a leader could read this slide and not realize that it evoked the existence of a mortal risk” .

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