This is the first of a series of articles on the design of simple graphs – graphs you could draw with pencil and ruler but are now more likely to be produced using software. You can find examples in the book Plain Figures1 covering the presentation of statistics by graphs and tables. Despite that and other sources of advice, simple two-dimensional graph forms often fail to communicate as their maker intended – or so one assumes.
Tuesday 9 May was a busy news day. In the space of a few hours, journalists had two major stories to contend with: the firing of FBI director James Comey, and the retirement of US Census Bureau director John Thompson.
No matter the field, if a researcher is collecting data of any kind, at some point he is going to have to analyze it. And odds are he’ll turn to statistics to figure out what the data can tell him.
Consider the following problem: “The serum test screens pregnant women for babies with Down's syndrome. The test is a very good one, but not perfect. Roughly 1% of babies have Down's syndrome. If the baby has Down's syndrome, there is a 90% chance that the result will be positive. If the baby is unaffected, there is still a 1% chance that the result will be positive. A pregnant woman has been tested and the result is positive. What is the chance that her baby actually has Down's syndrome?”