Abstract isn’t the same as logical
Suppose, to copy a classic example, you are a checking license compliance for a pub and have to make sure only people 18 or older are drinking alcohol. There are four people present. Alice is drinking beer. Boris is drinking water. Chris is fifteen. Doris is 50. Do you need to:
For most people, this is pretty easy.
The Herald has an equivalent puzzle that has been made pointless and abstract, in terms of letters and numbers, and lots of people get it wrong. That’s fine, except the headline is “Card test reveals how logical you are.” Manipulating conditional implications abstractly is a useful specialised skill, but it’s not the same as logic. In a similar way, manipulating probabilities symbolically is a useful specialised skill, but it’s not the same as understanding risk.
When it’s just a game, as in the story, this isn’t a big deal. But when you have a real question, communicating it so that it’s easy to answer rather than pointlessly hard does matter.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »