The Truthful Art (Ch7 & Ch8)  - MariaAguilarV/JMM-622-Infographics-and-Data-Visualization GitHub Wiki

Continuing with our weekly readings from the Truthful Art, this time, in chapter 7 and 8, Cairo goes deeper into statistics. Now we are on my world, how exciting! As an engineer, I’ve spent a few years with a wide range of math classes, which I started remembering when reading these chapters. It is very common to see averages when people want to illustrate or explain something; however, this is not the only information that we should look when exploring data. Cairo talks about 2 methods of numerical summaries of spread to analyze the variation of our data: the standard deviation and percentiles. Once we calculate the standard deviation, we can even compare 2 distributions that have different ranges calculating the standard score (or z-score). These values can be illustrated using histograms, strip plots or box plots (sometimes also called a box-and-whisker plot to show quartiles). I also found interesting how the size of the sample is important when analyzing data; in fact, to illustrate this point, the author talks about “The Galton probability box” which shows that the larger the sample is, the less variation it will have. When I read this example I couldn’t stop thinking “how beautiful math is”, isn’t it?
Cairo also talks about the time series chart and what elements we should pay attention to explore the change in one or more continuous variables. These elements are the trend, the seasonality and the noise; and, sometimes, showing one or a combination of two of these elements could reveal very interesting information. We can also use the seasonal subseries chart when we want to compare 2 series.

It is interesting how the author shows different types of graphics that can help us to deliver statistical information and make it understandable to our audience. I started the post talking about my years in engineering learning math, and, yes, I learned all those formulas to calculate statistic values, but we didn’t pay much attention on what graphics to use and when should we show them; it is a perspective that I was definitely missing!