About objectivity in information graphics
Imagine you have an important task. It is explain how to fix or substitute a bone. Scientifically, the information is hard to understand because you have some phisical, fisiological, mechanical, biological and contextual aspects to study case by case to decide which alternative of treatment is fittable. If the work is to communicate, the main problem is decide what is important or what is unnecessary to the story.
The problem is editing. And to edit is to make choice about what is information and what is noise. The word noise is wonderful to make it is clear. The concept is explored in the book The signal and the noise by Nate Silver. He discuss about how is difficult and confusing to be right when we have many data available. In my opinion and supported by my professional experience, editing have more chance to hit full, when you translate each main concept in a question.
One question is a block of the knowledge about the subject. Because this, if you have a level of water in a reservatory, for exemple, changing to up or down during some period, an graph of evolution, called line chart, is a better way to show it. Put perspectives, different periods, cuts of scale, colors to each point… all of it is noise. The golden rule is: one question each time.
But I need to explain how some periods are different and why levels above the average are so dangerous! Ok, you can do this. But tells a story is make a path through individual good and clear answers. If you have some questions, maybe the best way to answer all is make some sequencial different charts, diagrams or maps, one completing the other. Or, put some informations together, but the hierarchy will be very well executed. People must to see that only one thing is important and the other things are contextual.
Of course, connect all answers logically is an obligation to the group of the visual explanations does the job well. And the link between each piece have to be obvious.
How many questions you have to explain something to your target? My piece of advice to build a useful visual explanation is: first, make a list of questions. It will be a structure of the script to your story and each chart will be focused in its own natural way to show the information.