Chart showing Donald Trump Popularity and Unpopularity over time

How to Use Comparisons to Understand Data

Posted by Ray Poynter, 15 October 2018. Most individual numbers do not mean very much. In many cases, in order to see the real meaning in most data, you need comparisons. For example, if I tell you that the Belgian cyclist Eddy Merckx won 11 Grand Tours, you will no doubt guess that he was a good rider. But, when I tell you that 11 is the most any rider has ever won, and that only one other rider has won 10, and only one other rider has even won 8, then you start to get a sense of how special Eddy Merckx’s was. So, this post focuses on how to use comparisons to understand the story in the data, and how to use comparisons to communicate the story in the data. How Popular/Unpopular is Donald Trump Nate Silver’s FiveFiftyEight.com provides a wealth of data on US sports and politics and provides a really good example of how to use comparisons in their regularly updated series ‘How popular/unpopular is Donald Trump?’ The chart below shows the picture on 12 October 2018, 631 days after Donald Trump took office in January 2017. Note, in the US the election for a new […]

Image of digits

How many significant digits should you display in your presentation?

Posted by Ray Poynter, 27 August 2018 Too many digits can obscure the story being communicated by numbers. Let’s consider a simple example from a trip to your gym and its hi-tech weighing machine. Perhaps the machine says that your weight is 101.7865 kilograms and that it should be 82 kilograms. The story is that you are about 20 kilograms too heavy. To see the story you need to focus on comparing 102 kilograms with 82, not 101.7865 with 82. If your presentation or report displays too many digits you will obscure the story you are trying to communicate. The choice about the right number of digits to display is the choice about how many significant digits to display – the topic of this post. Digits Obscure – Example 1 Consider the table below, which is extracted from the ITU (International Telecommunication Union) and shows how many mobile phones there were in each of the countries displayed, from 2010 to 2017, per 100 people. If you click on the data tables they get bigger. The data shows four decimal places and is not very easy for most humans to quickly review. This data is not friendly for the analyst looking […]